SSM2135
20
18
16
V
S
= +5.0V
V
O
= 3.9V
5
4
R
L
= 2kΩ
OPEN-LOOP GAIN – V/µV
SUPPLY CURRENT – mA
14
12
10
8
6
4
2
0
–75
–50
–25
V
S
=
±18V
3
V
S
=
±15V
V
S
= +5.0V
R
L
= 600Ω
2
1
0
0
25
50
75
100
125
–75
–50
–25
0
25
50
75
100
125
TEMPERATURE –
°
C
TEMPERATURE –
°
C
Figure 25. Open-Loop Gain vs. Temperature
Figure 27. Supply Current vs. Temperature
70
V
S
= +5V
5
500
GAIN-BANDWIDTH PRODUCT – MHz
65
GBW
60
θm
4
INPUT BIAS CURRENT – nA
400
V
S
= +5.0V
300
V
S
=
±15V
200
PHASE MARGIN – Degrees
3
55
2
100
50
–75
–50
–25
0
25
50
75
100
TEMPERATURE –
°
C
1
125
0
–75
–50
–25
0
25
50
75
100
125
TEMPERATURE –
°
C
Figure 26. Gain Bandwidth Product and Phase Margin vs.
Temperature
Figure 28. Input Bias Current 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.
REV. D
–7–
AD [ ANALOG DEVICES ]
