Keithley 7012-S Service Manual

SECTION
4
Principles of
Operation
The
voltage
drop
across
the bad
is 20V
(5niA
x
4k2 =
20V).
This
voltage
is
scaled down to
2V
and
invertei
This 2V
is fed
back
(via
V
FEEDBACK)
to
U15A
and
U5B. The non-4nverting
(+)
input
of U15B
will go posi
tive keeping CR12
reverse-biased. As a
result, the
+V
CLAMP remains off.
Current from ±10V REF will flow into
the
+1 CLAMP,
which is
turned on (remember, the other clamps are
off).
As
a
result, the feedback
configuration and the
1 DAC
output will apply
a
voltage
to
the
error
amplifier
(U14)
that will effect a constant
+5mA output current.
Main
To Output
Stage
Figure
42.
Simplified
Schematic of
VII Control
and Readback
43

Keithley 7012-S Specifications

General

Brand	Keithley
Model	7012-S
Category	Measuring Instruments
Language	English