Revision A – August 12, 2004
S3160 – 2.5 Gbps Wide Bandwidth Transimpedance Amplifier
Data Sheet
The output of the transimpedance stage is converted
to a differential signal by the combination of the output
stage and a bias block. This bias block averages the
output of the transimpedance stage and establishes
the DC input reference for the output stage. The band-
width of this circuit is set by an on-chip capacitor, but
DETAILED DESCRIPTION
Figure 2 depicts the overall block diagram of the
S3160 transimpedance amplifier. The amplifier cir-
cuitry consists of a transimpedance stage and an
output driver stage with a 6 dB gain. The transimped-
ance amplifier converts the photodiode photocurrent to
a voltage. The photodiode can be biased by connect-
ing it to the RBYPASS pin or it can be connected
can be reduced by adding an off-chip capacitor, C
.
FILT
This bandwidth corresponds to the low frequency -3 dB
cutoff of the TIA. Increasing the value of C
will
FILT
directly to V
.
CC
reduce the low frequency -3 dB cutoff. With no C
capacitor added it will be at 45 kHz.
FILT
The amplifier gain is linear for an input of up to 300 µA.
Above that the transimpedance of the input stage is
reduced by the action of the schottky diode, to prevent
overdrive of the output stage. The output of the output
stage begins to fully limit when the input current
reaches 700 µA. The output voltage is limited at 1000
mV, differential, peak to peak.
Figure 2. S3160 Detailed Block Diagram
V
CC
CFILT
(OPTIONAL)
RBYPASS
V
FILT
CC
100 Ω
OUTP
OUTN
X 2
IIN
BIAS
1500 Ω
GND
2
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AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
