SGM8902 Datasheet, PDF (8/14 Pages) SG Micro Corp – Capless 2Vrms to 3Vrms Line Driver

SGM8902
Capless 2Vrms to 3Vrms Line Driver
with Adjustable Gain
APPLICATION INFORMATION
Decoupling Capacitors
The SGM8902 is a capless line driver amplifier that requires adequate power supply decoupling to ensure that the
noise and total harmonic distortion (THD) are low. A good low equivalent-series-resistance (ESR) ceramic capacitor,
typically 1µF, placed as close as possible to the device V_DD lead, works best. Placing this decoupling capacitor close
to the SGM8902 is important for the performance of the amplifier. For filtering lower frequency noise signals, a 10µF
or larger capacitor placed near the audio power amplifier would also help, but it is not required in most applications
because of the high PSRR of this device.
Gain Setting Resistors Ranges
The gain setting resistors, R_IN and R_FB, must be chosen so that noise, stability and input capacitor size of the
SGM8902 are kept within acceptable limits. Voltage gain is defined as R_FB divided by R_IN.
Selecting values that are too low demands a large input AC coupling capacitor, C_IN. Selecting values that are too
high increases the noise of the amplifier. Table 1 lists the recommended resistor values for different gain settings.
Table 1. Recommended Resistor Values
INPUT RESISTOR
VALUE, RIN
22kΩ
20kΩ
33kΩ
10kΩ
FEEDBACK RESISTOR
VALUE, RFB
22kΩ
30kΩ
68kΩ
100kΩ
DIFFERENTIAL INPUT
GAIN
1.0V/V
1.5V/V
2.1V/V
10.0V/V
INVERTING
INPUT GAIN
-1.0V/V
-1.5V/V
-2.1V/V
-10.0V/V
NON INVERTING
INPUT GAIN
2.0V/V
2.5V/V
3.1V/V
11.0V/V
C_IN
R_IN
-IN
Differential
Input
R_FB
_
+
+IN
C_IN
R_IN
R_FB
Figure 1. Differential Input
C_IN
R_IN
-IN
Inverting
R_FB
_
+
Figure 2. Inverting
C_X
R_IN
R_FB
_
Non
Inverting
+
+IN
C_IN
R_X
Figure 3. Non-Inverting
SG Micro Corp
www.sg-micro.com
DECEMBER 2016
8