REV. E

–8–

SSM2135

TEMPERATURE – C

20

0

–75

125

–50

–25

0

25

50

75

100

18

12

8

4

2

16

14

10

6

TPC 24. Open-Loop Gain vs. Temperature

TEMPERATURE – C

70

65

50

–75

125

–50

–25

0

25

50

75

100

60

55

5

4

1

3

2

GBW

m

TPC 25. Gain Bandwidth Product and Phase Margin

vs. Temperature

TEMPERATURE – C

5

4

0

–75

125

–50

–25

0

25

50

75

100

3

2

1

TPC 26. Supply Current vs. Temperature

TEMPERATURE – C

500

400

0

–75

125

–50

–25

0

25

50

75

100

300

200

100

TPC 27. Input Bias Current vs. Temperature

APPLICATION INFORMATION

The SSM2135 is a low voltage audio amplifier that has excep-

tionally low noise and excellent sonic quality even when driving

loads as small as 25

W. Designed for single supply use, the

SSM2135’s inputs common-mode and output swing to 0 V.

Thus with a supply voltage at 5 V, both the input and output

will swing from 0 V to 4 V. Because of this, signal dynamic

range can be optimized if the amplifier is biased to a 2 V reference

rather than at half the supply voltage.

The SSM2135 is unity-gain stable, even when driving into a fair

amount of capacitive load. Driving up to 500 pF does not cause

any instability in the amplifier. However, overshoot in the fre-

quency response increases slightly.

The SSM2135 makes an excellent output amplifier for 5 V only

audio systems such as a multimedia workstation, a CD output

amplifier, or an audio mixing system. The amplifier has large

output swing even at this supply voltage because it is designed

to swing to the negative rail. In addition, it easily drives load

impedances as low as 25

W with low distortion.

The SSM2135 is fully protected from phase reversal for inputs

going to the negative supply rail. However, internal ESD protec-

tion diodes will turn on when either input is forced more than

0.5 V below the negative rail. Under this condition, input cur-

rent in excess of 2 mA may cause erratic output behavior, in

which case a current limiting resistor should be included in the

offending input if phase integrity is required with excessive input

voltages. A 500

W or higher series input resistor will prevent

phase inversion even with the input pulled 1 V below the nega-

tive supply.

“Hot” plugging the input to a signal generally does not present a

problem for the SSM2135, assuming the signal does not have

any voltage exceeding the device’s supply voltage. If so, it is

advisable to add a series input resistor to limit the current, as

well as a Zener diode to clamp the input to a voltage no higher

than the supply.