Gennum Corporation GC509 Datasheet

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Class A Amplifier with

3 Independent Gain Blocks

GC509 DATA SHEET

FEATURES

• 145

µA typical current drain

• low noise and distortion

• 1.0 to 5 VDC operating range

• 2 independent preamplifiers

• Class A output stage

• variable transducer current

• 4 k

Ω microphone decoupling resistor

STANDARD PACKAGING

• 10 pin MICROpac

• 10 pin PLID

®

• 10 pin SLT

• Chip (61 x 55 mils)
Au Bump

DESCRIPTION

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.

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.

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 (R
simply place an external R

). To increase the bias current in the transducer,

E

resistor from pin 8 to ground,

E

thereby decreasing the equivalent emitter resistance and
increasing the current.

V

B

6

V

MIC

R

MIC

5

21K

4

A IN

- A

A OUT

3

B IN

2

All resistors in ohms, all capacitors in Farads unless otherwise
stated

- B

10

B OUT

9

C IN

- C

1
GND

C OUT

7

R

E

8

R

E

BLOCK DIAGRAM

Document No. 510 - 70 - 3

GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. [phone] fax: [phone]

Japan Branch: A-302, Miyamae Vi llage, 2–10–42 M i yamae, Suginami–ku, Tokyo 168, Japan tel. [phone] fax [phone]

ABSOLUTE MAXIMUM RATINGS

PIN CONNECTION

PARAMETER VALUE / UNITS
Supply Voltage 5V DC
Power Dissipation 25 mW
Operating Temperature -10o to + 40oC
Storage Temperature -20o to + 70oC

V

MIC

A IN

B IN

A OUT

GND

5

V

6

B

C OUT

R

E

C IN

B OUT

101

CAUTION

CLASS 1 ESD SENSITIVITY

ELECTRICAL CHARACTERISTICS

Conditions: Frequency = 1 kHz, Temperature = 25oC, Supply Voltage = 1.3 VDC

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Amplifier Current I

Transducer Current I

Maximum Transducer Current I

Input Bias Current I

AMP

TRANS

TRANS(MAX)

BIAS

R

= ∞ 200 275 350 µA

E

RE= 0 Ω 2 - - mA

RFA = 1M, RFB = 1M -50 0 50 nA

80 145 210 µ A

Input Referred Noise IRN NFB 0.2 to 10kHz at 12dB/Oct - 1 2 µVRMS

Harmonic Distortion THD S1 = b, V

Voltage Gain A

V

S1 = b, V

= 500 mVRMS - 1 4 %

OUT

= 500 mVRMS 70 73 76 dB

OUT

Stable with Battery Resistance Stability RB = 22 Ω - - 22 Ω
Resistance (RB) to:

Emitter Bias Voltage (Pin 8) V

Microphone Resistance R

On Chip Emitter Resistor R

Preamp Current Drive Capability I

All switches remain as shown in Test Circuit unless otherwise stated in CONDITIONScolumn.

RE

MIC

E

OUT

- 55 - mV
3 4 5 kΩ

- 200 - Ω

- 30 - µA

RB = 4.7

1.3 VDC

R

MIC

5

6

V

OUT

510 - 70 - 3

a

V



R

S

3.3K

IN

CS



S1

b

1.0

4

- A

3

2

1kHz

R

56.2K

FA =

2.7K

All resistors in ohms, all capacitors in Farads unless otherwise stated

1.0

- B

10

R

47.5K

FB =

Fig.1 Test Circuit

2

1.0

RL = 1K

- C

21K

7

8

R

E

9

1

=

R

E

0.015

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47.5