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FEATURES Four Independent Channels Voltage IN, Voltage OUT No External Parts Required 8 MHz Bandwidth Four-Quadrant Multiplication Voltage Output; W = (X x Y)/2.5 V 0.2% Typical Linearity Error on X or Y Inputs Excellent Temperature Stability: 0.005% 2.5 V Analog Input Range Operates from 5 V Supplies Low Power Dissipation: 150 mW typ Spice Model Available APPLICATIONS Geometry Correction in High-Resolution CRT Displays Waveform Modulation & Generation Voltage Controlled Amplifiers Automatic Gain Control Modulation and Demodulation GENERAL DESCRIPTION The MLT04 is a complete, four-channel, voltage output analog multiplier packaged in an 18-pin DIP or SOIC-18. These complete multipliers are ideal for general purpose applications such as voltage controlled amplifiers, variable active filters, "zipper" noise free audio level adjustment, and automatic gain control. Other applications include cost-effective multiple-channel power calculations (I x V), polynomial correction generation, and low frequency modulation. The MLT04 multiplier is ideally suited for generating complex, high-order waveforms especially suitable for geometry correction in high-resolution CRT display systems.
Four-Channel, Four-Quadrant Analog Multiplier MLT04
FUNCTIONAL BLOCK DIAGRAM 18-Lead Epoxy DIP (P Suffix) 18-Lead Wide Body SOIC (S Suffix)
W1 GND1 X1 Y1 V
CC
1 2 3 4 5 6 7 8 9
18
W4
17 GND4 16 15 X4 Y4
MLT-04 9 8 7 6 5 4 3 2 18 10 11 12 13 14 15 16 17 MLT04
14 V EE 13 12 11 10 Y3 X3 GND3 W3
Y2 X2 GND2 W2
W = (X
* Y)/2.5V
Fabricated in a complementary bipolar process, the MLT04 includes four 4-quadrant multiplying cells which have been lasertrimmed for accuracy. A precision internal bandgap reference normalizes signal computation to a 0.4 scale factor. Drift over temperature is under 0.005%/C. Spot noise voltage of 0.3 V/Hz results in a THD + Noise performance of 0.02% (LPF = 22 kHz) for the lower distortion Y channel. The four 8 MHz channels consume a total of 150 mW of quiescent power. The MLT04 is available in 18-pin plastic DIP, and SOIC-18 surface mount packages. All parts are offered in the extended industrial temperature range (-40C to +85C).
100
40 V CC = +5V V EE = -5V T A = +25C 8.9MHz -3dB 0
10
O - Phase Degrees
THD + NOISE - %
90
VCC = +5V V = -5V
EE
20
TA = +25C
Av GAIN - dB
Av (X OR Y) 0
1 LPF = 500kHz THDX: X = 2.5VP, Y = +2.5V DC
O (X OR Y) -20 X & Y MEASUREMENTS SUPERIMPOSED: X = 100mV RMS, Y = 2.5V DC Y = 100mV RMS, X = 2.5V DC 10k 100k 1M FREQUENCY - Hz 10M
-90
0.1 THDY: Y = 2.5VP, X = +2.5V DC
-40 1k
0.01
100M
10
100
1k 10k FREQUENCY - Hz
100k
1M
Figure 1. Gain & Phase vs. Frequency Response
Figure 2. THD + Noise vs. Frequency
REV. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703
MLT04-SPECIFICATIONS (V
Parameter MULTIPLIER PERFORMANCE 1 Total Error2 X Total Error2 Y Linearity Error2 X Linearity Error2 Y Total Error Drift Total Error Drift Scale Factor3 Output Offset Voltage Output Offset Drift Offset Voltage, X Offset Voltage, Y DYNAMIC PERFORMANCE Small Signal Bandwidth Slew Rate Settling Time AC Feedthrough Crosstalk @ 100 kHz OUTPUTS Audio Band Noise Wide Band Noise Spot Noise Voltage Total Harmonic Distortion Open Loop Output Resistance Voltage Swing Short Circuit Current INPUTS Analog Input Range Bias Current Resistance Capacitance SQUARE PERFORMANCE Total Square Error POWER SUPPLIES Positive Current Negative Current Power Dissipation Supply Sensitivity Supply Voltage Range Symbol EX EY LEX LEY TCEX TCEY K ZOS TCZOS XOS YOS BW SR tS FTAC CTAC EN EN eN THDX THDY ROUT VPK ISC IVR IB RIN CIN ESQ ICC IEE PDISS PSSR VRANGE
CC
= +5 V, VEE = -5 V, VIN = 2.5 VP, RL = 2 k, TA = +25C unless otherwise noted.)
Min -5 -5 -1 -1 0.38 -50 -50 -50 Typ 2 2 0.2 0.2 0.005 0.005 0.40 10 50 10.5 10.5 8 53 1 -65 -90 76 380 0.3 0.1 0.02 40 3.3 30 +2.5 10 Max 5 5 +1 +1 0.42 50 50 50 Units % FS % FS % FS % FS %/C %/C 1/V mV V/C mV mV MHz V/s s dB dB V rms V rms V/Hz % % VP mA V A M pF % FS 20 20 200 10 5.25 mA mA mW mV/V V
Conditions -2.5 V < X < +2.5 V, Y = +2.5 V -2.5 V < Y < +2.5 V, X = +2.5 V -2.5 V < X < +2.5 V, Y = +2.5 V -2.5 V < Y < +2.5 V, X = +2.5 V X = -2.5 V, Y = 2.5 V, TA = -40C to +85C Y = -2.5 V, X = 2.5 V, TA = -40C to +85C X = 2.5 V, Y = 2.5 V, TA = -40C to +85C X = 0 V, Y = 0 V, TA= -40C to +85C X = 0 V, Y = 0 V, TA= -40C to +85C X = 0 V, Y = 2.5 V, TA = -40C to +85C Y = 0 V, X = 2.5 V, TA = -40C to +85C VOUT = 0.1 V rms VOUT = 2.5 V VOUT = 2.5 V to 1% Error Band X = 0 V, Y = 1 V rms @ f = 100 kHz X = Y = 1 V rms Applied to Adjacent Channel f = 10 Hz to 50 kHz Noise BW = 1.9 MHz f = 1 kHz f = 1 kHz, LPF = 22 kHz, Y = 2.5 V f = 1 kHz, LPF = 22 kHz, X = 2.5 V VCC = +5 V, VEE = -5 V
30
3.0
GND = 0 V X=Y=0V
-2.5 2.3 1 3 5 15 15 150 4.75
X=Y=1 VCC = 5.25 V, VEE = -5.25 V VCC = 5.25 V, VEE = -5.25 V Calculated = 5 V x ICC + 5 V x IEE X = Y = 0 V, VCC = 5% or VEE = 5% For VCC & VEE
NOTES 1 Specifications apply to all four multipliers. 2 Error is measured as a percent of the 2.5 V full scale, i.e., 1% FS = 25 mV. 3 Scale Factor K is an internally set constant in the multiplier transfer equation W = K x X x Y. Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS* Supply Voltages VCC, VEE to GND Inputs XI, YI Outputs WI Operating Temperature Range Maximum Junction Temperature (T J max) Storage Temperature Lead Temperature (Soldering, 10 sec) Package Power Dissipation Thermal Resistance JA PDIP-18 (N-18) SOIC-18 (SOL-18)
ORDERING INFORMATION* 7 V VCC, VEE VCC, VEE -40C to +85C +150C -65C to +150C +300C (TJ max-TA)/JA 74C/W 89C/W Model MLT04GP MLT04GS MLT04GS-REEL MLT04GBC Temperature Range -40C to +85C -40C to +85C -40C to +85C +25C Package Description Package Option
18-Pin P-DIP N-18 18-Lead SOIC SOL-18 18-Lead SOIC SOL-18 Die
*For die specifications contact your local Analog sales office. The MLT04 contains 211 transistors.
*Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification are not implied.
-2-
REV. B
MLT04
FUNCTIONAL DESCRIPTION The MLT04 is a low cost quad, 4-quadrant analog multiplier with single-ended voltage inputs and voltage outputs. The functional block diagram for each of the multipliers is illustrated in Figure 3. Due to packaging constraints, access to internal nodes for externally adjusting scale factor, output offset voltage, or additional summing signals is not provided.
+VS X1, X2, X3, X4
ANALOG MULTIPLIER ERROR SOURCES Multiplier errors consist primarily of input and output offsets, scale factor errors, and nonlinearity in the multiplying core. An expression for the output of a real analog multiplier is given by:
V O = ( K + K ){(VX + X OS )(V Y + Y OS ) + ZOS + f ( X , Y )}
where:
MLT04
0.4 W1, W2, W3, W4
G1, G2, G3, G4
K K VX XOS VY YOS ZOS (X, Y)
= = = = = = = =
Multiplier Scale Factor Scale Factor Error X-Input Signal X-Input Offset Voltage Y-Input Signal Y-Input Offset Voltage Multiplier Output Offset Voltage Nonlinearity
Y1, Y2, Y3, Y4 -VS
Executing the algebra to simplify the above expression yields expressions for all the errors in an analog multiplier:
Figure 3. Functional Block Diagram of Each MLT04 Multiplier
Term Each of the MLT04's analog multipliers is based on a Gilbert cell multiplier configuration, a 1.23 V bandgap reference, and a unityconnected output amplifier. Multiplier scale factor is determined through a differential pair/trimmable resistor network external to the core. An equivalent circuit for each of the multipliers is shown in Figure 4.
VCC W OUT
Description True Product Scale-Factor Error Linear "X" Feedthrough Due to Y-Input Offset Linear "Y" Feedthrough Due to X-Input Offset Output Offset Due to X-, Y-Input Offsets Output Offset Nonlinearity
Dependence on Input Goes to Zero As Either or Both Inputs Go to Zero Goes to Zero at VX, VY = 0 Proportional to VX Proportional to VY Independent of VX, VY Independent of VX, VY Depends on Both V X, VY. Contains Terms Dependent on VX, VY, Their Powers and Cross Products
KVXVY KVYVY VXYOS VYXOS XOSYOS ZOS (X, Y)
INTERNAL BIAS
XIN GND YIN
22k
22k
22k SCALE FACTOR
200A VEE
200A
200A
200A
200A
200A
Figure 4. Equivalent Circuit for the MLT04
Details of each multiplier's output-stage amplifier are shown in Figure 5. The output stages idles at 200 A, and the resistors in series with the emitters of the output stage are 25 . The output stage can drive load capacitances up to 500 pF without oscillation. For loads greater than 500 pF, the outputs of the MLT04 should be isolated from the load capacitance with a 100 resistor.
VCC
As shown in the table, the primary static errors in an analog multiplier are input offset voltages, output offset voltage, scale factor, and nonlinearity. Of the four sources of error, only two are externally trimmable in the MLT04: the X- and Y-input offset voltages. Output offset voltage in the MLT04 is factory-trimmed to 50 mV, and the scale factor is internally adjusted to 2.5% of full scale. Input offset voltage errors can be eliminated by using the optional trim circuit of Figure 6. This scheme then reduces the net error to output offset, scale-factor (gain) error, and an irreducible nonlinearity component in the multiplying core.
+VS I
50k 50k
25 W OUT 25
-VS
100mV FOR XOS, YOS TRIM CONNECT TO SUM NODE OF AN EXT OP AMP
Figure 6. Optional Offset Voltage Trim Configuration
VEE
Figure 5. Equivalent Circuit for MLT04 Output Stages
REV. B
-3-
MLT04
Feedthrough In the ideal case, the output of the multiplier should be zero if either input is zero. In reality, some portion of the nonzero input will "feedthrough" the multiplier and appear at the output. This is caused by the product of the nonzero input and the offset voltage of the "zero" input. Introducing an offset equal to and opposite of the "zero" input offset voltage will null the linear component of the feedthrough. Residual feedthrough at the output of the multiplier is then irreducible core nonlinearity. Typical X- and Y-input feedthrough curves for the MLT04 are shown in Figures 7 and 8, respectively. These curves illustrate MLT04 feedthrough after "zero" input offset voltage trim. Residual X-input feedthrough measures 0.08% of full scale, whereas residual Y-input feedthrough is almost immeasurable.
100
VERTICAL - 5mV/DIV
90
10 0%
X-INPUT: 2.5V @ 10Hz Y-INPUT: +2.5V YOS NULLED T = +25C A
HORIZONTAL - 0.5V/DIV
Figure 9. X-Input Nonlinearity @ Y = +2.5 V
100
VERTICAL - 5mV/DIV
90
VERTICAL - 5mV/DIV
X-INPUT: 2.5V @ 10Hz YOS NULLED TA = +25C
100 90
10 0%
10 0%
X-INPUT: 2.5V @ 10Hz Y-INPUT: -2.5V YOS NULLED T = +25C A
HORIZONTAL - 0.5V/DIV
HORIZONTAL - 0.5V/DIV
Figure 7. X-Input Feedthrough with YOS Nulled
Figure 10. X-Input Nonlinearity @ Y = -2.5 V
100
VERTICAL - 5mV/DIV
VERTICAL - 5mV/DIV
90
Y-INPUT: 2.5V @ 10Hz XOS NULLED TA = +25C
100 90
Y-INPUT: 2.5V @ 10Hz X-INPUT: +2.5V XOS NULLED TA = +25C
10 0%
10 0%
HORIZONTAL - 0.5V/DIV
HORIZONTAL - 0.5V/DIV
Figure 8. Y-Input Feedthrough with XOS Nulled
Nonlinearity Multiplier core nonlinearity is the irreducible component of error. It is the difference between actual performance and "best-straightline" theoretical output, for all pairs of input values. It is expressed as a percentage of full scale with all other dc errors nulled. Typical X- and Y-input nonlinearities for the MLT04 are shown in Figures 9 through 12. Worst-case X-input nonlinearity measured less than 0.2%, and Y-input nonlinearity measured better than 0.06%. For modulator/demodulator or mixer applications it is, therefore, recommended that the carrier be connected to the X-input while the signal is applied to the Y-input.
Figure 11. Y-Input Nonlinearity @ X = +2.5 V
100
VERTICAL - 5mV/DIV
90
Y-INPUT: 2.5V @ 10Hz X-INPUT: -2.5V XOS NULLED T = +25C A
10 0%
HORIZONTAL - 0.5V/DIV
Figure 12. Y-Input Nonlinearity @ X = -2.5 V
-4-
REV. B
Typical Performance Characteristics - MLT04
12 9 6 TA = +25C V = 5V
S
180 135 90 45 GAIN 0 -45 PHASE -90 PHASE = 68.3 @ 7.142 MHz 100k 1M FREQUENCY - Hz -135 -180 10M
PHASE - Degrees
VX = 100mV VY = +2.5V
OUTPUT NOISE VOLTAGE - 100V/DIV
100 90
GAIN -dB
NBW = 10Hz -50kHz TA = +25C
3 0 -3 -6
10 0%
-9 -12 10k TIME = 10ms/DIV
Figure 13. Broadband Noise
Figure 16. X-Input Gain and Phase vs. Frequency
12 9 6
OUTPUT NOISE VOLTAGE - 625V/DIV
NBW = 1.9MHz TA = +25C
180 V S = 5V V X = +2.5V T A = +25C 135 90 45 GAIN 0 -45 PHASE -90 PHASE = 68.1 @ 8.064 MHz 100k 1M FREQUENCY - Hz -135 -180 10M
V Y = 100mV
3
100 90
0 -3 -6
10 0%
-9 -12 10k
TIME = 10ms/DIV
Figure 14. Broadband Noise
Figure 17. Y-Input Gain and Phase vs. Frequency
10000 VS = 5V TA = +25C
Hz NOISE DENSITY - nV/
8 6 4 CL= 220pF 2 CL= 320pF
CL= 560pF
AV GAIN - dB
1000
0 -2 -4 -6 -8 -10 VS = 5V RL = 2k TA = +25C NO CL CL= 100pF
100
0 10 100 1k 10k FREQUENCY - Hz 100k 1M
-12 1k 10k 100k 1M FREQUENCY - Hz 10M 100M
Figure 15. Noise Density vs. Frequency
Figure 18. Amplitude Response vs. Capacitive Load
REV. B
-5-
PHASE - Degrees
GAIN -dB
MLT04 - Typical Performance Characteristics
0 VS = 5V -20
FEEDTHROUGH - dB
VERTICAL - 50mV/DIV
TA = +25C
100 90
X-INPUT = +2.5V RL = 10k TA = +25C
-40
VX = 0V VY = 1Vpk
-60 VY = 0V VX = 1Vpk
10 0%
-80
TIME - 100ns/DIV
-100 1k 10k 100k FREQUENCY - Hz 1M 3M
Figure 22. Y-Input Small-Signal Transient Response, CL = 30 pF
X-INPUT = +2.5V RL = 10k TA = +25C
Figure 19. Feedthrough vs. Frequency
VERTICAL - 50mV/DIV
100 90
0 TA = 25C VS = 5V VX = 2.5Vpk VY = +2.5VDC
CROSSTALK - dB
-20
10 0%
-40
-60
TIME - 100ns/DIV
-80
Figure 23. Y-Input Small-Signal Transient Response, CL = 100 pF
-100
-120 1k 10k
Figure 20. Crosstalk vs. Frequency
VERTICAL - 1V/DIV
100k FREQUENCY - Hz
1M
10M
100 90
10 0%
2.0 1.5 1.0 0.5
AV GAIN - dB
X-INPUT: +2.5V RL = 10k TA = +25C
Y = 100mV RMS X = 2.5VDC
VS = 5V RL = 2k TA = +25C
TIME = 100ns/DIV
0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 1k 10k 100k 1M 10M 100M FREQUENCY - Hz X = 100mV RMS Y = 2.5VDC
Figure 24. Y-Input Large-Signal Transient Response, CL = 30 pF
100
VERTICAL - 1V/DIV
90
10 0%
X-INPUT: +2.5V RL = 10k TA = +25C TIME = 100ns/DIV
Figure 21. Gain Flatness vs. Frequency
Figure 25. Y-Input Large-Signal Transient Response, CL = 100 pF
-6-
REV. B
MLT04
1
9 VS = 5V VX = +2.5V
-3dB-BANDWIDTH - MHz
80
8 -3dB BW
75
THD + NOISE - %
0.1
7
0.01
VS = 5V RL = 2k T A = +25C fO = 1kHz FLPF = 22kHz Y-INPUT X = +2.5VDC
70
PHASE @ -3dB BW 6 65
0.001 0.1 1 INPUT SIGNAL LEVEL - Volts P-P 10
5 -75
-50
-25
25 50 TEMPERATURE - C
0
75
100
60 125
Figure 26. THD + Noise vs. Input Signal Level
Figure 29. Y-Input Gain Bandwidth vs. Temperature
0.3
MAXIMUM OUTPUT SWING - Volts p-p
8
V = +2.5V, -2.5V V +2.5V X Y V = +2.5V, -2.5V V +2.5V
Y X
Vs = 5V
0.2
LINEARTY ERROR - %
7 6 5 4 3 2 1 TA = +25C RL = 2k VS = 5V 1% DISTORTION
0.1
0
-0.1
-0.2
-0.3 -75
0
-50 -25 0 25 50 75 100 125
1k
10k
100k FREQUENCY - Hz
1M
10M
TEMPERATURE - C
Figure 27. Linearity Error vs. Temperature
Figure 30. Maximum Output Swing vs. Frequency
9 V = 5V S V = 100mV
X Y
80
4.5 4.0
V = +2.5V
-3dB-BANDWIDTH - MHz OUTPUT SWING - Volts
8
75
PHASE @ -3dB BW - Degrees
3.5 3.0 2.5 2.0
POSITIVE SWING
-3dB BW 7 70
NEGATIVE SWING 1.5 1.0 0.5 VS = 5V TA = +25C 10 100 1k 10k
PHASE @ -3dB BW 6 65
5 -75
-50
-25
0
25
50
75
100
60 125
0 LOAD RESISTANCE -
TEMPERATURE - C
Figure 28. X-Input Gain Bandwidth vs. Temperature
Figure 31. Maximum Output Swing vs. Resistive Load
REV. B
-7-
PHASE @ -3dB BW - Degrees
X-INPUT Y = +2.5VDC
V = 100mV Y
MLT04
300 SS = 1000 MULTIPLIERS 250 TA = +25C V = 5V
S
0.407 VS = 5V NO LOAD 0.406
X = 2.5V YOS @ X = 2.5V XOS @ Y = 2.5V
200
UNITS
SCALE FACTOR - 1/V
0.405
150
0.404
100
50
0.403
0 -12.5 -10
-7.5
-5 -2.5 0 2.5 5 OFFSET VOLTAGE - mV
7.5
10
12.5
0.402 -75
-50
-25
0
25
50
75
100
125
TEMPERATURE - C
Figure 32. Offset Voltage Distribution
400
Figure 35. Scale Factor vs. Temperature
6 VS = 5V 4 XOS, Y = 2.5V 2
VOS - mV
UNITS
T = +25C 350 300 250 200 150 SS = 1000 MULTIPLIERS
A
VS = 5V VX = VY = 0V
0
-2 YOS, X = 2.5V -4
100 50 0
-6 -75
-50
-25
0 25 50 TEMPERATURE - C
75
100
125
-15
-12
-9
-6
-3
0
3
6
9
12
15
OUTPUT OFFSET VOLTAGE - mV
Figure 33. Offset Voltage vs. Temperature
400 SS = 1000 MULTIPLIERS 350 300 250 TA = +25C
Figure 36. Output Offset Voltage (ZOS) Distribution
10 V = 5V
OUTPUT OFFSET VOLTAGE - mV
VS = 5V
s
5
UNITS
200 150 100 50 0 0.395 0.3975 0.400 0.4025 0.405 0.4075 0.410 0.4125 0.415
0
-5
-10 -75
-50
-25
SCALE FACTOR - 1/V
0 25 50 TEMPERATURE - C
75
100
125
Figure 34. Scale Factor Distribution
Figure 37. Output Offset Voltage (ZOS) vs. Temperature
-8-
REV.B
MLT04
17 VS = 5V NO LOAD VX = VY = 0
SUPPLY CURRENT - mA
15 12 X +3
OUTPUT VOLTAGE OFFSET - mV
9 6 3 0 -3 -6 -9 -12 X -3 X
16
15
14
13 -75
-15
-50
-25
0
25
50
75
100
125
0
200
400
600
800
1000
TEMPERATURE - C
HOURS OF OPERATION AT +125C
Figure 38. Supply Current vs. Temperature
Figure 41. Output Voltage Offset (ZOS) Distribution Accelerated by Burn-in
0.424
100 TA = +25C
0.420 0.416
SCALE FACTOR - 1/V
POWER SUPPLY REJECTION - dB
80
VS = 5V
X +3 0.412 0.408 0.404 0.400 0.396 X -3 0.392 0.388 X
+PSRR 60 -PSRR 40
20
0 100
0.384
1k 10k FREQUENCY - Hz 100k 1M
0
200
400
600
800
1000
HOURS OF OPERATION AT +125C
Figure 39. Power Supply Rejection vs. Frequency
Figure 42. Scale Factor (K) Distribution Accelerated by Burn-in
1.25 1.0 0.75
LINEARITY ERROR - %
X +3
0.50 0.25 0 -0.25 -0.50 -0.75 X -3 -1.0 -1.25 0 200 400 600 800 1000 HOURS OF OPERATION AT +125C X
Figure 40. Linearity Error (LE) Distribution Accelerated by Burn-in
REV. B
-9-
MLT04
APPLICATIONS The MLT04 is well suited for such applications as modulation/ demodulation, automatic gain control, power measurement, analog computation, voltage-controlled amplifiers, frequency doublers, and geometry correction in CRT displays. Multiplier Connections Figure 43 llustrates the basic connections for multiplication. Each of the four independent multipliers has single-ended voltage inputs (X, Y) and a low impedance voltage output (W). Also, each multiplier has its own dedicated ground connection (GND) which is connected to the circuit's analog common. For best performance, circuit layout should be compact with short component leads and well-bypassed supply voltage feeds. In applications where fewer than four multipliers are used, all unused analog inputs must be returned to the analog common. The equation shows a dc term at the output which will vary strongly with the amplitude of the input, V IN. The output dc offset can be eliminated by capacitively coupling the MLT04's output with a high-pass filter. For optimal spectral performance, the filter's cutoff frequency should be chosen to eliminate the input fundamental frequency. A source of error in this configuration is the offset voltages of the X and Y inputs. The input offset voltages produce cross products with the input signal to distort the output waveform. To circumvent this problem, Figure 45 illustrates the use of inverting amplifiers configured with an OP285 to provide a means by which the X- and Y-input offsets can be trimmed.
P1 50k -5V R5 500k
+5V XOS TRIM R2 10k
W1
1 2
W1 GND1 X1 Y1
W4 18 GND4 17
W4
R1 10k
2 3
3
+
1/4 MLT04
W1 C1 100pF VO RL 10k
+
A1
1 2 0.4 1
X1 Y1 +5V 0.1F Y2 X2
3 4 5
X4 16
X4 Y4
VIN
A1, A2 = 1/2 OP285 5
MLT04
Y4 15 VEE 14 Y3 13 X3 12
+
A2 7 4 +
10 11 12 13 14 15 16 17 9 8 7 6 5 4 3 2 VCC 18
-5V Y3 X3 0.1F
R3 10k R6 500k -5V 6
6 Y2 7 X2 8 GND2 W2
GND3
11 W3
R4 10k YOS TRIM +5V
W2
9
W3 10
P2 50k
W1-4 = 0.4 (X1-4
* Y1-4)
Figure 45. Frequency Doubler with Input Offset Voltage Trims
Feedback Divider Connections The most commonly used analog divider circuit is the "inverted multiplier" configuration. As illustrated in Figure 46, an "inverted multiplier" analog divider can be configured with a multiplier operating in the feedback loop of an operational amplifier. The general form of the transfer function for this circuit configuration is given by: R2 VIN VO = -2.5 V x x R1 V X Here, the multiplier operates as a voltage-controlled potentiometer that adjusts the loop gain of the op amp relative to a control signal, VX. As the control signal to the multiplier decreases, the output of the multiplier decreases as well. This has the effect of reducing negative feedback which, in turn, decreases the amplifier's loop gain. The result is higher closed-loop gain and reduced circuit bandwidth. As VX is increased, the output of the multiplier increases which generates more negative feedback -- closed-loop gain drops and circuit bandwidth increases. An example of an "inverted multiplier" analog divider frequency response is shown in Figure 47.
Figure 43. Basic Multiplier Connections
Squaring and Frequency Doubling As shown in Figure 44, squaring of an input signal, V IN, is achieved by connecting the X-and Y-inputs in parallel to produce an output of VIN2/2.5 V. The input may have either polarity, but the output will be positive.
+5V 0.1F
VIN
X
+
0.4
1/4 MLT04
W W = 0.4 VIN2
GND
Y
+
0.1F
-5V
Figure 44. Connections for Squaring
When the input is a sine wave given by V IN sin t, the squaring circuit behaves as a frequency doubler because of the trigonometric identity:
(VIN sin t )2 V 2 1 = IN (1 - cos 2 t ) 2.5V 2.5V 2
-10-
REV. B
MLT04
1/4 MLT04 +
3 X1
1/4 MLT04 +
VX
D1 1N4148
3
X1
W1
1
0.4
2
GND1
W1
1
0.4
2
R2 10k
+
R1 10k VIN 2
Y1 4
R1 10k V
IN
R2 10k 4
Y1
2
OP113 6
3
+
VIN VX
VO
OP113 6
3
V
+
-2.5V * VIN
O
VO = -2.5V *
VO =
Figure 46. "Inverted-Multiplier" Configuration for Analog Division
90 80 70 60 AVOL OP113
GAIN - dB
50 VX = 0.025V 40 30 20 10 0 100 VX = 2.5V VX = 0.25V
Voltage-Controlled Low-Pass Filter The circuit in Figure 49 illustrates how to construct a voltagecontrolled low-pass filter with an analog multiplier. The advantage with this approach over conventional active-filter configurations is that the overall characteristic cut-off frequency, O, will be directly proportional to a multiplying input voltage. This permits the construction of filters in which the capacitors are adjustable (directly or inversely) by a control voltage. Hence, the frequency scale of a filter can be manipulated by means of a single voltage without affecting any other parameters. The general form of the circuit's transfer function is given by:
VO VIN
10k 100k FREQUENCY - Hz 1M 10M
1k
R2 1 = - R1 R2 + R1 2.5RC + 1 s R1 V X
Figure 47. Signal-Dependent Feedback Makes Variables Out of Amplifier Bandwidth and Stability
Although this technique works well with almost any operational amplifier, there is one caveat: for best circuit stability, the unitygain crossover frequency of the operational amplifier should be equal to or less than the MLT04's 8 MHz bandwidth. Connection for Square Rooting Another application of the "inverted multiplier" configuration is the square-root function. As shown in Figure 48, both inputs of the MLT04 are wired together and are used as the output of the circuit. Because the circuit configuration exhibits the following generalized transfer function: R2 VO = -2.5 x xVIN R1 the input signal voltage is limited to the range -2.5 V VIN < 0. To prevent circuit latchup due to positive feedback or input signal polarity reversal, a 1N4148-type junction diode is used in series with the output of the multiplier.
In this circuit, the ratio of R2 to R1 sets the passband gain, and the break frequency of the filter, LP, is given by: R1 V X LP = R1 + R2 2.5RC
X1
3
+
+
1/4 MLT04
R 10k C 80pF
VX GND1 2 0.4 W1 1
2
+
R1 10k VIN 4 Y1 R2 10k
3
+
A1
1
VO
A1 = 1/2 OP285
VO VIN fLP = VX 10RC
=- 1+S
1 5RC VX
; fLP = MAX @ VX = 2.5V
Figure 48. Connections for Square Rooting
Figure 49. A Voltage-Controlled Low-Pass Filter For example, if R1 = R2 = 10 k , R = 10 k , and C = 80 pF,
REV. B
-11-
MLT04
then the output of the circuit has a pole at frequencies from 1 kHz to 100 kHz for VX ranging from 25 mV to 2.5 V. The performance of this low-pass filter is illustrated in Figure 20. OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
18-Lead Epoxy DIP (P Suffix)
30
PIN 1 18 10 0.280 (7.11) 0.240 (6.10) 1 9
20
10
GAIN - dB
0.210 (5.33) MAX 0.160 (4.06) 0.115 (2.93)
0.925 (23.49) 0.845 (21.47)
0.015 (0.38) MIN 0.130 (3.30) MIN
0.325 (8.25) 0.300 (7.62)
0
- 10
V = 0.025V
X
0.25V
2.5V
0.022 (0.558) 0.014 (0.356) 0.100 (2.54) BSC 0.070 (1.77) 0.045 (1.15) SEATING PLANE
15 0
0.015 (0.38) 0.008 (0.20)
- 20
- 30 10
100
1k
10k 100k FREQUENCY - Hz
1M
10M
Figure 50. Low-Pass Cutoff Frequency vs. Control Voltage, VX
18
18-Lead Wide-Body SOL (S Suffix)
10 0.2992 (7.60) 0.2914 (7.40) 0.4193 (10.65) 0.3937 (10.00)
With this approach, it is possible to construct parametric biquad filters whose parameters (center frequency, passband gain, and Q) can be adjusted with dc control voltages.
PIN 1 1 9
0.4625 (11.75) 0.4469 (11.35)
0.1043 (2.65) 0.0926 (2.35)
0.0291 (0.74) x 45 0.0098 (0.25)
0.0118 (0.30) 0.0040 (0.10)
0.0500 (1.27) BSC
0.0192 (0.49) 0.0138 (0.35)
0.0125 (0.32) 0.0091 (0.23)
8 0
0.0500 (1.27) 0.0157 (0.40)
-12-
REV. B
PRINTED IN U.S.A.
C1845-18-10/93

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