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Low Current Preamplifier with Output Limiting
GK504 - DATA SHEET
FEATURES * designed to drive Class D integrated receivers * adjustable peak clipper * low current drain * low noise and distortion * low external parts count www..com * two low noise preamplifiers * transconductance output stage * mid supply referenced output * preamp A for Gain Trim or Telecoil STANDARD PACKAGING * 10 pin MICROpac * 10 pin PLID(R) * 10 pin SLT * Chip ( 56 x 84 mils) Au Bump DESCRIPTION The GK504 is Gennum's proprietary low current preamplifier designed to drive the Class D series receivers. It consists of two independent single-ended, low noise inverting amplifiers, a symmetrical peak clipping, mid-supply referenced, transconductance output stage, and an on-chip microphone decoupling resistor. Blocks A and B typically have an open loop voltage gain of 53 dB, with the closed loop gain set by the ratio of the feedback resistor to source impedance. It is recommended that the maximum closed loop gain be 20 dB lower than the open loop gain. All blocks of the device are internally bias compensated preventing any DC current flow via external feedback resistors. Without this compensation, audible scratchiness would be present during changes in Volume Control settings. It is acceptable to DC-couple blocks A and B of the device, however the third stage must be AC coupled in order to maintain DC bias requirements. The major advantage of the GK504 over other preamplifiers is the electronic MPO adjustment. Since conventional MPO is not possible in the class D receivers, it is provided electronically. The maximum output swing is easily set using an RMPO resistor. The receiver output level is thus limited, preventing it from exceeding the discomfort level.
V
MIC
3
R MIC
4
VB
R 2
P1
A IN
A
B
C
5
C
OUT
R
P2
1
10
9
8
7
6
A OUT B IN
U.S. Patent No.07/354,327
B OUT CIN
R MPO GND
BLOCK DIAGRAM
Revision Date; May 1998 Document No. 520 - 47 - 05
GENNUM CORPORATION P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3 tel. +1 (905) 632-2996 Web Site: www.gennum.com E-mail: hipinfo@gennum.com
ABSOLUTE MAXIMUM RATINGS Parameter
Supply Voltage Power Dissipation Operating Temperature Storage Temperature
PIN CONNECTIONS Value / Units
5 VDC 25 mW -10C to + 40C -20C to + 70C
COUT VB VMIC AIN AOUT 1 10 5 6 GND RMPO CIN BOUT BIN
CAUTION
CLASS 1 ESD SENSITIVITY
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ELECTRICAL CHARACTERISTICS
Positive Current corresponds to current INTO the pin, Negative Current corresponds to current OUT of the pin, Conditions: Frequency = 1 kHz, VP - Pin voltage measured with conditions as shown in Test Circuit. Temperature 25o C.
PARAMETER Supply Current Input Referred Noise Distortion On-Chip Microphone Resistance
SYMBOL IAMP IRN THD RMIC
CONDITIONS
MIN 165
TYP 240 2 <1.0 4
MAX 315 5
UNITS A VRMS % k
NFB 0.2 - 10 kHz at 12 dB/oct -
-
3 STAGES A and B
Input Bias Current Input Bias Voltage Output Swing Lo Max Output Current Capability Open Loop Voltage Gain
IBIAS VBIAS VOL IMAX AVOL
RF=1M (Note 1)
-25 500
0 590 280 -30 53
25 650 590 -45 -
nA mV mV A dB
RF=1M (Note 2)
200 -15 46
OUTPUT STAGE Voltage Gain (Pin 8 to Pin 5) Gain Loss (Pin 8 to Pin 5) Maximum Output Level MPO Range Output Impedance AV GAIN MPO MPO ZOUT VINAC = -52 dBV, RMPO= 0 VIN = -62 dBV, RMPO = 50k,Note 3 VINAC = -22 dBV, RMPO = 0 VINAC = -22 dBV,RMPO = (0 to 10k) 14 -14.5 12 19 16 0 -12.5 14 24 18 2.5 -10.5 16 29 dB dB dBV dB K
All parameters and conditions remain as shown in Test Circuit unless otherwise specified in Conditions column. NOTES: 1. IBIAS = (Vp(1,9 ) - Vp(1,9 )[RF=1M])/1M 2. VOL = VBIAS -Vp(1,9) [VIN DC=+1A,RF=1M,IL=+15A] 3. GAIN = (V OUT / VIN [VIN =-62dBV, RMPO=0] )- (VOUT / VIN [VIN =-62dBV, RMPO=50k]
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2
RMIC 3
IBIAS
4 R A B C R P2 1 10
I BIAS
VB=1.3 VDC
IAMP
P1
VIN DC
5
01
V
2
OUT
9
8 10
7 RMPO=10k
6
RL 50k
RF=0
RF=0
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IL=0
VINDC IL=0
VINAC= 0VRMS 1kHz
All resistors in ohms, all capacitors in F, unless otherwise stated.
Fig. 1 Test Circuit
RMIC 3 48k 4
9 BASE CURRENT COMPENSATION 2 1 33k 10
5
2.5k
48k 6
All resistors in ohms, all capacitors in F, unless otherwise stated.
7
8
Fig. 2 Functional Schematic
3
520 - 47 - 05
RMIC 10 MIC CIN 022 3 R A B C R
P1
VB =1.3 VDC 4
5 33n
P2
2
Class D Integrated Receiver 10
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1 10 9 8 7 RMPO 10k 100k R GT 10k R VC 100k 33n 6
All resistors in ohms, all capacitors in F, unless otherwise stated.
Fig. 3
Typical Hearing Instrument Application
RMIC 10 3 R 2 A B C R
P1
4
VB =1.3 VDC
5 33n
P2
Class D Integrated Receiver 10
047
1
10
9
8
7 RMPO 10k
6
MIC
100k R GT 022
10k R VC
100k 33n
+
All resistors in ohms, all capacitors in F, unless otherwise stated.
Fig. 4
Typical Hearing Instrument Application
520 - 47 - 05
4
RMIC 10 RMIC 3k92 CS 022 2 A B C R 3 R
P1
VB =1.3 VDC 4
5 01
P2
+
BUFFER
-
AC SOURCE 50
1
10
9
8
7 R MPO =0
RL 50k 6 AC VOLTMETER
100k
10k R VC
100k 01
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R GT
All resistors in ohms, all capacitors in F, unless otherwise stated. This circuit as shown was used to generate the following graphs unless otherwise stated.
Fig. 5
Characterization Circuit
-5 -15 -25
-10
R VC = 100k
-14 -18
RMPO= 0
OUTPUT (dBV)
OUTPUT (dBV)
-35 -45 -55 -65 -75 -85 -140
R VC = 33k
RMPO = 3.3k
-22 -26 -30 -34
R MPO = 10k
R VC = 10k
R VC = 3.3k
-38 -120 -100 -80 -60 -40 -20 -100 -80 -60 -40 -20
INPUT (dBV)
INPUT (dBV)
Fig. 6 I/O for Various RVC Values
Fig. 7 MPO for Various RMPO Values
2 0 -2
10
CIN = 0.22 CIN = 0.1 THD (%)
20K
9 8 7 6 5 4 3 2 1
RELATIVE OUTPUT (dB)
-4 -6 -8 -10 -12 -14 -16 -18 -20 20
CIN = 0.047
CIN = 0.033
200
2K
0 -90
-86
-82
-78
-74
-70
FREQUENCY (Hz)
INPUT (dBV)
Fig. 8 Frequency Response for Various CIN Values
Fig. 9 Distortion vs Input Level (RGT = RVC = 100k)
5
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10 -12 -10 -30 -16
RELATIVE SUPPLY CURRENT (A)
OUTPUT (dBV)
1 10 100 1k 10k 100k
-50 -70 -90 -110
-20 -24
-28 -32
-130 -36 -50 -40 -30 -20 -10 0
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RMPO ()
INPUT (dBV)
Fig. 10 Change in Supply Current vs RMPO
Fig. 11 I/O for Amplifier C (as in Fig. 1)
55
-10 -14
MAXIMUM OUTPUT (dBV)
-18 -22 -26 -30 -34 -38 -42
50
GAIN (dB)
1M
1M 10 1.3V
45
2.2k 10
VOUT
PREAMP
40
VAC
0
10
100
1k
10k
100k
35 10
100
1k
10k
100k
RMPO ()
FREQUENCY (Hz)
Fig. 12 Maximum Output vs RMPO (as in Fig. 1, VINAC= -15dBV)
Fig. 13 Preamplifiers A and B Open Loop Voltage Gain
DOCUMENT IDENTIFICATION: DATA SHEET The product is in production. Gennum reserves the right to make changes at any time to improve reliability, function or design, in order to provide the best product possible. REVISION NOTES:
Updated to Data sheet
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. (c) Copyright July 1990 Gennum Corporation. All rights reserved.
Printed in Canada.
520 - 47 - 05
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