SSM2135SZ Datasheet, PDF (12/16 Pages) Analog Devices – Dual Single-Supply Audio Operational Amplifier

SSM2135
Single Supply Differential Line Driver
Signal distribution and routing is often required in audio systems,
particularly portable digital audio equipment for professional
applications. Figure 35 shows a single-supply line driver circuit
that has differential output. The bottom amplifier provides a
2 V dc bias for the differential amplifier to maximize the output
swing range. The amplifier can output a maximum of 0.8 V rms
signal with a 5 V supply. It is capable of driving into 600 Ω line
termination at a reduced output amplitude.
1kΩ
5V _{10µF + 0.1µF}
100µF
AUDIO IN
1kΩ
10kΩ
2V
1µF
1/2
SSM2135
DIFFERENTIAL
AUDIO OUT
1kΩ
1/2
SSM2135
2.5kΩ
0.1µF
100Ω
5V
1/2
SSM2135
5V
7.5kΩ
5kΩ
Figure 35. Single-Supply Differential Line Driver
Single-Supply Differential Line Receiver
Receiving a differential signal with minimum distortion is
achieved using the circuit in Figure 36. Unlike a difference
amplifier (a subtractor), the circuit has a true balanced input
impedance regardless of input drive levels; that is, each input
always presents a 20 kΩ impedance to the source. For best
common-mode rejection performance, all resistors around the
differential amplifier must be very well matched. Best results
can be achieved using a 10 kΩ precision resistor network.
20kΩ
5V _{10µF + 0.1µF}
DIFFERENTIAL
AUDIO IN
20kΩ
1/2
SSM2135
20kΩ _20kΩ
20kΩ
1µF
1/2
10Ω ^10µF
2V
SSM2135
5V
AUDIO
OUT
100Ω
1/2
SSM2135
7.5kΩ
5V
5kΩ
0.1µF
2.5kΩ
Figure 36. Single-Supply Balanced Differential Line Receiver
Pseudoreference Voltage Generator
For single-supply circuits, a reference voltage source is often
required for biasing purposes or signal offsetting purposes. The
circuit in Figure 37 provides a supply splitter function with low
output impedance. The 1 μF output capacitor serves as a charge
reservoir to handle a sudden surge in demand by the load as
well as providing a low ac impedance to it. The 0.1 μF feedback
capacitor compensates the amplifier in the presence of a heavy
capacitive load, maintaining stability.
The output can source or sink up to 12 mA of current with a
5 V supply, limited only by the 100 Ω output resistor. Reducing
the resistance increases the output current capability. Alternatively,
increasing the supply voltage to 12 V also improves the output
drive to more than 25 mA.
V+ = 5V TO 12V
R3
2.5kΩ
C1
0.1µF
R1
5kΩ
R4
1/2
SSM2135
100kΩ
V+
2
OUTPUT
C2
R2
1µF
5kΩ
Figure 37. Pseudoreference Generator
Rev. G | Page 12 of 16