Class A Amplifier with 3 Independent Gain Blocks GC509 DATA SHEET DESCRIPTION FEATURES • 145 µA typical current drain The GC509 is a Class A amplifier utilizing Gennum’s proprietary low voltage JFET technology. It consists of two singleended, low noise inverting gain blocks, a Class A output stage, and an on-chip microphone decoupling resistor. • low noise and distortion • 1.0 to 5 VDC operating range • 2 independent preamplifiers Blocks A and B typically have an open loop voltage gain of 56 dB, with the closed loop gain set by the ratio of the feedback resistor to the 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. • Class A output stage • variable transducer current • 4 kΩ microphone decoupling resistor STANDARD PACKAGING • 10 pin MICROpac The output stage of the GC509 is a Class A current drive. It has a fixed reference voltage of typically 55 mV at pin 8 of the device. The current that flows in the transducer is the ratio of the 55 mV reference voltage and the on-chip emitter resistor (RE ). To increase the bias current in the transducer, simply place an external RE resistor from pin 8 to ground, thereby decreasing the equivalent emitter resistance and increasing the current. • 10 pin PLID ® • 10 pin SLT • Chip (61 x 55 mils) Au Bump VB VMIC 5 6 RMIC 21K 4 A IN -B -A -C 7 8 C OUT RE RE 2 10 3 A OUT B IN B OUT 9 1 C IN GND All resistors in ohms, all capacitors in Farads unless otherwise stated BLOCK DIAGRAM Document No. 510 - 70 - 3 GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 Japan Branch: A-302, M i yamae Vi l l age, 2–10–42 M i yamae, Suginami–ku, Tokyo 168, Japan tel. (905) 632-2996 fax: (905) 632-5946 tel. (03) 3334-7700 fax (03) 3247-8991 ABSOLUTE MAXIMUM RATINGS PIN CONNECTION PARAMETER VALUE / UNITS Supply Voltage 5V DC VMIC Power Dissipation 25 mW A IN C OUT B IN RE Operating Temperature -10o to + 40oC Storage Temperature -20o to + 70oC 5 6 A OUT VB C IN GND 1 10 B OUT CAUTION CLASS 1 ESD SENSITIVITY ELECTRICAL CHARACTERISTICS Conditions: Frequency = 1 kHz, Temperature = 25o C, Supply Voltage = 1.3 VDC PARAMETER SYMBOL CONDITIONS Amplifier Current I AMP Transducer Current I TRANS RE= ∞ Maximum Transducer Current I TRANS(MAX) RE= 0 Ω Input Bias Current I BIAS RFA = 1M, RFB = 1M Input Referred Noise IRN Harmonic Distortion MIN TYP MAX UNITS 80 145 210 µA 200 275 350 µA 2 - - mA nA -50 0 50 NFB 0.2 to 10kHz at 12dB/Oct - 1 2 µVRMS THD S1 = b, VOUT = 500 mVRMS - 1 4 % Voltage Gain AV S1 = b, VOUT = 500 mVRMS 70 73 76 dB Stable with Battery Resistance Resistance (RB) to: Stability RB = 22 Ω - - 22 Ω Emitter Bias Voltage (Pin 8) VRE - 55 - mV Microphone Resistance R MIC 3 4 5 kΩ On Chip Emitter Resistor RE - 200 - Ω Preamp Current Drive Capability I OUT - 30 - µA All switches remain as shown in Test Circuit unless otherwise stated in CONDITIONScolumn. RB = 4.7 1.3 VDC 5 RS VOUT RL = 1K 21K VIN a CS 3.3K 1.0 b 6 RMIC 4 -B -A -C 7 S1 8 RE 2 10 3 9 1 0.015 1kHz RFB = 47.5K RFA = 56.2K 2.7K 1.0 1.0 All resistors in ohms, all capacitors in Farads unless otherwise stated Fig.1 Test Circuit 2 510 - 70 - 3 RE = 47.5 5 6 RMIC 21K 2 BASE CURRENT COMPENSATION 10 7 9 8 33K 3 4 RE 1 Fig. 2 Functional Schematic VB = 1.3 VDC 6 RMIC 1.0 5 ED1913 RLAC 21K -A RS = 3.9K CS 0.22 -B -C 7 4 8 RE 2 3 10 100K RGT 9 1 100K 120 0.1 5.6K RVC All resistors in ohms, all capacitors in Farads unless otherwise stated. Gain of stage A = 20 Log 10 RGT RS Gain of stage B = 20 Log 10 RVC 5.6K Gain of stage C = 20 Log RLAC//21K 10 RE/120 Fig. 3 Typical Hearing Aid Circuit 3 510 - 70 - 3 0 4 RVC = 100K -10 CS = 0.22µ 0 RVC = 47K RELATIVE OUTPUT (dB) OUTPUT (dBV) -20 -30 R VC -40 = 22K RVC = 10K -50 -60 RVC = 3.3K -70 -80 -140 CS = 0.1µ -4 -8 CS = 0.047µ -12 CS = 0.033µ -16 -20 -120 -100 -80 -60 20 -40 200 10 60 0 55 -10 50 -20 45 -30 -40 40 35 -50 30 -60 25 0.7 0.8 0.9 1 1.1 1.2 1.3 20 10 1.4 100 SUPPLY VOLTAGE (V) 10K 100K Fig. 7 Preamplifier Open Loop Frequency Response 30 RELATIVE AMPLIFIER CURRENT (µA) 10 RELATIVE TRANSDUCER CURRENT (µA) 1K FREQUENCY (Hz) Fig. 6 Gain vs Supply Voltage 5 0 -5 -10 -15 -20 20k Fig. 5. Closed Loop Frequency Response with Various CS Values GAIN (dB) RELATIVE GAIN (dB) Fig. 4 I/O Curves at Various RVC Settings -70 2k FREQUENCY (Hz) INPUT (dBV) 20 10 0 -10 -20 -30 -40 -20 -10 0 10 20 30 40 50 -20 -10 0 10 20 30 40 50 TEMPERATURE (o C) TEMPERATURE ( oC) Fig. 8 Transducer Current vs Temperature Fig. 9 Amplifier Current vs Temperature DOCUMENT IDENTIFICATION PRODUCT PROPOSAL This data has been compiled for market investigation purposes only, and does not constitute an offer for sale. REVISION NOTES Changes to standard packaging. Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. © Copyright July 1989 Gennum Corporation. All rights reserved. Printed in Canada. PRELIMINARY DATA SHEET The product is in a development phase and specifications are subject to change without notice. Revision Date: July 1992 4 510 - 70 - 3 ADVANCE INFORMATION NOTE This product is in development phase and specifications are subject to change without notice. Gennum reserves the right to remove the product at any time. Listing the product does not constitute an offer for sale. 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.