Feedbackelements - Keithley 595 Instruction Manual

THEORY OF OPERATION
7.5.3 Feedback Elements
Range switching for the current function is accomplished
with relays K302, K304, DO6 and K307. Capacitors are con-
various resistors and capacitors are switched in as feedback
netted in pamllel with the feedback resistors to avoid stabili-
around the compound op-amp to configure the pre+mpli-
ty problems when shunt capacitance is high and to set the
fier for specific rtiges 6f the current and capacitance func-
response time constant and bandwidth.
tions. The configuration of the feedback elements md relay
switches are shown in Figure 7-12. Able 7-1 shows the state
of the relay switches for each range. C322 and C302 are
The ZERO CHECK relay (K3Ol) is also configured as a feed-
onswitched feedback capacitors which combine to be the
back element, isolating the preamplifier from the input by
lOpF feedback element. K345 and K303 switch the 91pF ~~AoMa.
(C303) and 1OOOpF (C304) capacitors respectively for the
other capacitance ranges.
Table 7-l. Relay Switch Configuration
3mction Range
1 200/h
1 Zero Check X
Rels
303 K3D4
X
f
X
X
X
X
::
* *
-
307
-
1
X
X
T-
X = Relay Switch Closed
* = These relay switches may also be closed depending on range and
fUllCliOTl.
7-11