SSM2164SZ Analog Devices Inc, SSM2164SZ Datasheet - Page 8

• Manufacturer Part Number: SSM2164SZ
• Description: IC AMP AUDIO QUAD CLASSAB 16SOIC
• Manufacturer: Analog Devices Inc
• Type: Var Gain Ampr

Specifications of SSM2164SZ

• Amplifier Type: Audio
• Number Of Circuits: 4
• Current - Input Bias: 10nA
• Current - Supply: 6mA
• Voltage - Supply, Single/dual (±): 8 V ~ 36 V, ±4 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• No. Of Amplifiers: 4
• Bandwidth: 500kHz
• No. Of Channels: 1
• Supply Voltage Range: ± 4V To ± 18V
• Amplifier Case Style: SOIC
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +85°C
• Number Of Channels: 4
• Number Of Elements: 4
• Power Supply Requirement: Dual
• Voltage Gain Db: 20dB
• Unity Gain Bandwidth Product (typ): 500KHz
• Input Resistance: 0.005@±15VMohm
• Input Bias Current: 0.01@±15VnA
• Single Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (typ): ±5/±9/±12/±15V
• Power Supply Rejection Ratio: 90dB
• Rail/rail I/o Type: No
• Single Supply Voltage (min): Not RequiredV
• Single Supply Voltage (max): Not RequiredV
• Dual Supply Voltage (min): ±4V
• Dual Supply Voltage (max): ±18V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 16
• Package Type: SOIC N
• Current, Input Bias: ±10 nA
• Current, Supply: 6 mA
• Harmonic Distortion: 0.3 %
• Impedance, Thermal: 92 °C/W
• Number Of Amplifiers: Quad
• Slew Rate: 0.7
• Temperature, Operating, Range: -40 to +85 °C
• Voltage, Supply: ±4 to ±18 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• Current - Output / Channel: -
• -3db Bandwidth: -
• Slew Rate: -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -
• Lead Free Status / Rohs Status: Compliant

SSM2164
but higher noise, and the opposite is true for less current. The
increased noise is due to higher current noise in the gain core
transistors as their operating current is increased. THD has the
opposite relationship to collector current. The lower distortion
is due to the decrease in the gain core transistors’ emitter
impedance as their operating current increases.
This classical tradeoff between THD and noise in VCAs is
usually expressed as the choice of using a VCA in either Class A
or Class AB mode. Class AB operation refers to running a VCA
with less current in the gain core, resulting in lower noise but
higher distortion. More current in the core corresponds to
Class A performance with its lower THD but higher noise.
Figures 11 and 12 show the THD and noise performance of the
SSM2164 as the bias current is adjusted. Notice the two
characteristics have an inverse characteristic.
The quiescent current in the core is set by adding a single
resistor from the positive supply to the MODE pin. As the
simplified schematic shows, the potential at the MODE pin is
one diode drop above the ground pin. Thus, the formula for the
MODE current is:
With 15 V supplies, an R
current of 1.9 mA. Leaving the MODE pin open sets the
SSM2164 in Class AB with 30 A of current in the gain core.
Basic VCA Configuration
Figure 24 shows the basic application circuit for the SSM2164.
Each of the four channels is configured identically. A 30 k
resistor converts the input voltage to an input current for the
VCA. Additionally, a 500
capacitor must be added from each input to ground to ensure
stable operation. The output current pin should be maintained
at a virtual ground using an external amplifier. In this case the
OP482 quad JFET input amplifier is used. Its high slew rate,
wide bandwidth, and low power make it an excellent choice for
the current-to-voltage converter stage. A 30 k feedback
resistor is chosen to match the input resistor, giving unity gain
for a 0.0 V control voltage. The 100 pF capacitors ensure
stability and reduce high frequency noise. They can be
increased to reduce the low pass cutoff frequency for further
noise reduction.
For this example, the control voltage is developed using a
100 k potentiometer connected between +5 V and ground.
This configuration results in attenuation only. To produce both
gain and attenuation, the potentiometer should be connected
between a positive and negative voltage. The control input has
an impedance of 5 k . Because of this, any resistance in series
with V
the gain and attenuation is required, a buffered control voltage
should be used.
Notice that a capacitor is connected from the control input to
ground. Because the control port is connected directly to the
gain core transistors, any noise on the V
output noise of the VCA. Filtering the control voltage ensures
that a minimal amount of noise is introduced into the VCA,
allowing its full performance to be realized. In general, the
largest possible capacitor value should be used to set the filter at
C
will attenuate the control signal. If precise control of
I
MODE
B
of 7.5k gives Class A biasing with a
resistor in series with a 560 pF
(V ) 0.6V
R
B
C
pin will increase the
–8–
a low cutoff frequency. The main exception to this is in
dynamic processing applications, where faster attack or decay
times may be needed.
Low Cost, Four-Channel Mixer
The four VCAs in a single package can be configured to create a
simple four-channel mixer as shown in Figure 25. The inputs
and control ports are configured the same as for the basic VCA,
but the outputs are summed into a single output amplifier. The
OP176 is an excellent amplifier for audio applications because
of its low noise and distortion and high output current drive.
The amount of signal from each input to the common output
can be independently controlled using up to 20 dB of gain or as
much as 100 dB of attenuation. Additional SSM2164s could be
added to increase the number of mixer channels by simply
summing their outputs into the same output amplifier. Another
possible configuration is to use a dual amplifier such as the
OP275 to create a stereo, two channel mixer with a single
SSM2164.
V
V
V
V
IN1
IN2
IN3
IN4
100k
100k
100k
100k
+5V
+5V
+5V
+5V
Figure 24. Basic Quad VCA Configuration
30k
560pF
30k
30k
30k
560pF
560pF
560pF
1µF
1µF
1µF
1µF
500
500
500
500
V
I
V
V
V
I
I
I
IN
C
IN
IN
IN
C
C
C
–15V
3
2
6
7
11
10
14
15
9
AND BIASING CIRCUITRY
V–
0.1µF 0.1µF
POWER SUPPLY
8
GND
VCA1
VCA2
VCA3
VCA4
16
+15V
V+
1
12
13
4
MODE
5
R
B
I
I
I
I
(7.5k
(OPEN CLASSAB)
IOUT
IOUT
IOUT
IOUT
CLASS A)
OP482
OP482
OP482
OP482
100pF
100pF
100pF
100pF
1/4
1/4
1/4
1/4
30k
30k
30k
30k
REV. 0
V
V
V
V
OUT1
OUT2
OUT3
OUT4