15MHz, High Output Drive, High Precision,
Low Noise, Automotive Operational Amplifier
SGM8557H-1AQ
APPLICATIONS INFORMATION
Single-Supply Stereo Headphone Driver
A single-supply stereo headphone driver is shown in
Figure 1 as an example to explain the simplified design
procedure.
Bridge Amplifier
A bridge amplifier circuit which can provide 200mW at
3V is shown in Figure 2. Due to differential output, this
structure eliminates the large coupling capacitors in
Figure 1. The voltage gain is 10V/V and the gain can be
changed by changing R2.
RF
CIN
RIN
C1
0.1μF
Left
Audio Input
COUT
+
_
R1
16kΩ
R2
82kΩ
+
Headphone Jack
to 32Ω Stereo
Headset
SGM8557H-1AQ
3V
0.5VP-P
VBIAS
_
3V
R5
SGM8557H-1AQ
+
COUT
+
51kΩ
R3
10kΩ
+
CIN
RIN
Right
Audio Input
32Ω
fS =100Hz
_
SGM8557H-1AQ
R4
10kΩ
RF
C2
R6
_
0.1μF
51kΩ
Figure 1. Stereo Headphone Driver
+
SGM8557H-1AQ
In this circuit, CIN and RIN form a high-pass filter, the DC
bias is removed from the incoming signal. The -3dB
point of the high-pass filter is using Equation 1:
Figure 2. 200mW Bridge Amplifier at 3V
1
f-3dB
=
(1)
2πRINCIN
The gain of driver is -RF/RIN. The COUT and the load
impedance form a high-pass filter with the -3dB point
determined by Equation 2:
1
f-3dB
=
(2)
2πRLCOUT
SG Micro Corp
www.sg-micro.com
MAY 2022
8
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
