ATA01501
AGC Capacitor
It is important to select an external AGC capacitor of
high quality and appropriate size. The ATA00501D1C
has an on-chip 70 KW resistor with a shunt 4 pF
capacitor to ground. Without external capacitance the
chip will provide an AGC time constant of 280 nS. For
the best performance in a typical 51MB/s SONET
receiver, a minimum AGC capacitor of 56pF is
recommended. This will provide the minimum amount
of protection against pattern sensitivity and pulse
width distortion on repetitive data sequences during
high average optical power conditions. Conservative
design practices should be followed when selecting
an AGC capacitor, since unit to unit variability of the
internal time constant and various data conditions
can lead to data errors if the chosen value is too small.
Phase Response
At frequencies below the 3dB bandwidth of the device,
the transimpedance phase response is characteristic
of a single pole transfer function (as shown in the
Phase vs Frequency curve). The output impedance is
essentially resistive up to 1000 MHz.
180
200
V
OUT
220
240
I
IN
00501
0.5pF
50
100
150
Frequency (MHz)
Figure 14: Phase (IIN to VOUT)
PRELIMINARY DATA SHEET - Rev 1.6
8
08/2001
ANADIGICS [ ANADIGICS, INC ]
