SSM2135

REV. D

–7–

5

0

125

3

1

–50

2

4

100

75

50

25

0

–25

TEMPERATURE –

V

V

V

–75

Figure 27. Supply Current vs. Temperature

500

0

125

300

100

–50

200

400

100

75

50

25

0

–25

TEMPERATURE –

V

V

–75

Figure 28. Input Bias Current vs. Temperature

20

0

125

6

2

–50

4

12

8

10

14

16

18

100

75

50

25

0

–25

TEMPERATURE –

R

R

V

V

–75

Figure 25. Open-Loop Gain vs. Temperature

70

50

125

65

55

–50

60

75

100

50

25

0

–25

TEMPERATURE –

V

5

1

4

2

3

–75

GBW

θm

Figure 26. Gain Bandwidth Product and Phase Margin vs.

Temperature

APPLICATION INFORMATION

The SSM2135 is a low voltage audio amplifier that has

exceptionally low noise and excellent sonic quality even when

driving loads as small as 25

Ω. Designed for single supply use,

the SSM2135’s inputs common-mode and output swing to zero

volts. 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

frequency 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

Ω with low distortion.

The SSM2135 is fully protected from phase reversal for inputs

going to the negative supply rail. However, an internal ESD

protection diodes will turn “on” when either input is forced

more than 0.5 V below the negative rail. Under this condition,

input current 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

Ω or higher series input

resistor will prevent phase inversion even with the input pulled 1

volt below the negative 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.