Avago Technologies ACPL-224-500E - Manual (Page 45)

AV02-4387EN 42 Avago Technologies
Analog Applications
Description
This circuit with the HCPL-4562
Wideband Analog/Video Optocou-
pler functions as an ac-coupled iso-
lation amplifier that can be used for
coupling audio or video signals. The
input circuit biases the optocoupler
LED at a quiescent current of about
6 mA, determined primarily by resis-
tors R
1
, R
2
, and R
3
. Diode D
1
helps to
stabilize the operating point over
the operating temperature range.
An ac-coupled signal will modu late
the collector current of transistor
Q
1
and the optocoupler LED. The
output circuit consists of a simple
transresistance (current-in, voltage-
out) amplifier followed by a com-
mon-emitter amplifier stage.
Performance of Circuit
• Typical bandwidth: 13 MHz
• Nominal gain of circuit: 1
• Isolation­mode rejection: 46 dB at
1 kHz
• Overall nonlinearity: 0.5%
• Optocoupler input current range:
4 mA-8 mA
Benefits
• Simple solution for coupling au-
dio and video signals
References
1) HCPL-4562 Wideband Analog/
Video Optocoupler Technical
Data
2) Application Note 951-2, “Linear
Applications of Optocouplers”
Alternative Avago Parts
1) HCPL-2502, 6N135, 6N136 High
Speed Transistor Output Opto-
couplers
2) HCNW4562 Widebody Wide band
Analog/Video Optocoupler
3) HCPL-55XX, 4N55, HCPL-6530/1
Hermetically Sealed High Speed
Optocoupler
4) HCPL-05XX Small-Outline High
Speed Optocoupler
AC-Coupled Isolation Amplifier
7
5
6
8
2
3
4
1
HCPL-4562
+5 V
R5
5.6 k Ω
K
PD
Q
2
R7
470 Ω
I
D
2 µF
Q
3
R6
82 Ω
2
R4
18 k Ω
2 µF
Q
1
R3
330 Ω
1
R2
1.8 k Ω
+5 V
R1
2.2 k Ω
V
IN
I
F
D1
1N4150
Q1 2N3904
Q3 2N3904
GAIN 1 • K
PD
• R4 • R7 1
K
PD
= 0.0032 TYPICALLY
R3 R6
I
3
V OUT