Gennum Corporation LS509 Datasheet

Class A Amplifier with

3 Gain Blocks & Schottky Diodes

LS509 DATA SHEET

FEATURES

• 140 µA typical current drain

• low noise and distortion

• 1.0 to 5 VDC operating range

• independent preamplifier

• 2 DC coupled stages

• class A output stage

• variable transducer current

• Schottky diodes for MPO control

• 4 kΩ microphone decoupling resistor

STANDARD PACKAGING

• 10 pin PLID

• 10 pin SLT

• Chip (61 x 55 mils)

®

DESCRIPTION

The LS509 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, an on-chip microphone decoupling resistor and a
pair of Schottky diodes for symmetrical peak clipping.

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 LS509 is a Class A current drive.
It has a fixed reference voltage of typically 29 mV at pin 2
of the device. The current that flows in the transducer is the
ratio of the 29 mV reference voltage and the on-chip
emitter resistor (R
transducer, simply place an external RE resistor from pin
2 to ground, thereby decreasing the equivalent emitter
resistance and increasing the current.

). To increase the bias current in the

E

V

MIC

A I/P

Revision Date: January 2001

The LS509 also contains a pair of Schottky diodes in the
feedback configuration of the output stage, which provides
approximately 12 dB of MPO control.

V

B

8

7

R

MIC

A

-

6

5

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

A O/P B I/P B O/P GND

BLOCK DIAGRAM

B

-

4

MPO

9

21k

C

-

R

E

3

1

C O/P

10

R

E

2

Document No. 510 - 12 - 08

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

Web Site: www.gennum.com E-mail: [e-mail]

ABSOLUTE MAXIMUM RATINGS

PIN CONNECTION

PARAMETER VALUE/UNITS

Supply Voltage 5 V DC

Power Dissipation 25 mW
Operating Temperature Range -10°C to 40° C
Storage Temperature Range -20°C to 70° C

A OUT

B IN

B OUT

R

GND

5

E

1

6

10

CAUTION

CLASS 1 ESD SENSITIVITY

ELECTRICAL CHARACTERISTICS

VP - Pin voltage measured with conditions as shown in Test Circuit.
Positive current corresponds to current INTO the pin.
Negative current corresponds with current OUT of the pin.
Conditions: Frequency = 1 kHz, Temperature = 25°C, Supply Voltage V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Amplifier Current I
Transducer Current I
Maximum Transducer Current I
A Input Bias Voltage (pin 6) V
A Input Bias Current (pin 6) I
B Input Bias Current (pin 4) I
A O/P Voltage Swing-Hi (pin 5) V

A Output Swing-Lo (pin 5) V

A Open Loop Voltage Gain A
C Output Sat. Voltage (pin 10) V

A Output Current Capability (pin 5) A

Diode Voltage Drop V
Emitter Bias Voltage (pin 2) V
On-chip Microphone Resistor R
On-chip Emitter Resistor R

AMP

TRANS

TRANS (MAX)VP2

BIAS A

BIAS A

BIAS B

OH A

OL A

OL

SAT C

OUT

D

RE

MIC

E

RFA = 1 M (Note 1) -50 0 50 nA
RFB = 1 M (Note 2) -50 0 50 nA
VIN = 0.4 V DC, R

I

P5

I

IN

I

P5 =

RL = 1 kΩ, VP2 = 0 V - 100 180 mV

(S2 = b) R

= 0 V 2 - - mA

= -10 µA (Note 3)

= +1µA, RFA = ∞, 200 280 - mV

Input Referred Noise IRN NFB 0.2 to10kHz at 12dB/Oct - 1 - µVRMS
Harmonic Distortion THD V

All parameters and switches remain as shown in Test Circuit unless otherwise stated in "Conditions" column

Notes 1. I

2. I

3. V

4. V

5. V

BIAS A

BIAS B

OH A

OL A

=

D

= (VP6 -V

= (VP4 -V

=

=

(V

P6[RFA = 1M]

P4 [RFB = 1M]

(VP5-V

P5 [VIN = 0.4 VDC, RFA = ∞, IP5 = -10µA]

(VP5 -V

P5 [IIN = +1µA, RFA = ∞, I P5 =+10µA]

[Id = +(1.5 x ITRANS)] -VP10 [Id = +(0.5 x ITRANS)]

P10

)/1M

)/1M

OUT

)

)

= 1.3 V

B

75 140 205 µA

170 230 290 µA

500 570 650 mV

= ∞, 200 580 - mV

FA

+10 µA (Note 4)

46 56 - dB

- 30 - µA

= ∞, (Note 5) 140 265 325 mV

L

21.5 28.5 35.5 mV

345kΩ

90 125 160 Ω

= 500 mVRMS -1-%

)

A IN
V

MIC

V

B

MPO

C OUT

510 - 12 - 08

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