Tektronix FG 5010 User Manual

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Offset Current Generator
This circuit consists of amplifier U1631 ; field - effect tran
sistors Q1522
and Q1532 ;
transistors Q1521 , Q1611 ,
Q1531 , and
Q1621 ; plus related
components
.
Voltage from
the DAC is applied to the inverting input of U1631 , which
has a voltage gain of one .
Q1522 and Q1532 are part of a double - ended current
path that begins at the 26 V supply , through L1721 ,
R1621 , R1602 , CR1512 , etc. , through to the +26 V supply .
By
controlling the
voltage on the
gate of Q1522
, the current
through the series string is similarly controlled . Potentiom
eter
R1601 sets the
gain for the
positive offset
generator ;
R1602 sets the
gain for the
negative
offset
generator .
Since both offset generators cannot be on at once , tran
sistor current switches Q1521 - Q1611 and Q1531 - Q1621 di
vert current away from one or the other generator to
prevent simultaneous operation . If positive offset is select
ed , a is selected at U1521 pin 7 , and 1 at pin 6. This cuts
off Q1521 and Q1611 , which permits current to flow
INTRODUCTION
These three diagrams depict functions that are ancillary
to
the
signal - generating
loop
of the FG
5010.
Block
- level
discussions of these circuits are found elsewhere in the
description
, as
follows
:
Trigger
Circuits :
Phase Lock Circuits :
N Burst Circuits :
Refer to the Loop 2 Block
Diagram Description .
Refer to the Loop 2 Block
Diagram
Description .
Refer to the Sine Shaper Block
Diagram Description .
15 TRIGGER SECTION
Theory of Operation - FG 5010
TRIGGER
,
PHASE
LOCK ,
AND
N
BURST
CIRCUITS
Introduction
The Trigger Section receives the signal from the front
panel
TRIG / GATE
IN connector
, processes it ,
and sends the
processed
signal to the
Loop
1 circuits
, and
elsewhere
in the
Loop 2 circuits . The section also conveys triggering status
through the upper half of the offset string . The 1 at U1542
pin 6 causes Q1531 and Q1621 to conduct , diverting the
current away from the lower part of the string . Thus , the
Positive generator furnishes offset current in this example ,
and the Negative Generator does not .
Positive Offset Generator
This circuit consists of amplifier U1611 , transistor
Q1601 , and related components . This circuit operates much
like a conventional current regulation circuit . As mentioned
earlier , R1601 sets the gain . As current through R1601 is
changed by
changing the
offset
requirements , U1611
and
U1601 respond by increasing or decreasing the current
through
the
output
network .
Negative
Offset
Generator
This circuit consists of amplifier U1621 , transistor
Q1501 , and related components . Other than the polarity of
the
output
current , the circuit
is the same
as the
Positive
Offset generator . Refer to that description for more details .
to the CPU , and selects the trigger slope . The section con
sists of the Trig - Gate Input Amplifier , the Trig - Gate Slope
Selector , and the
Trigger Status
Sensor .
Trig - Gate Input Amplifier
This circuit consists of matched field - effect transistors
Q1020 and Q1022 ; transistors Q1032 , Q1030 , Q1036 ,
Q1034 ; buffers U1212A and U1212F ; plus related circuitry .
The trigger or gate signal is applied through front - panel con
nector J1650 to the input compensation network , which is
1 MS impedance or 50 £ impedance , depending on the con
nection of P1030 . From the network , the signal is fed to the
gate of FET Q1020 , which with Q1022 form a high - imped
ance
unity - gain
buffer . Diodes CR1021
and
CR1020 protect
the
input from
large
voltage
transients . Zener
diodes
VR1024 and VR1023 reduce the power dissipation across
Q1020 and Q1022 . The signal is taken from the source of
Q1020 and applied to the base of Q1032 , part of the input
differential pair
of a Schmitt trigger
circuit .
Transistors
Q1032 and Q1030 form a differential pair that switches the
current from R1031 . This differential pair drives a second
pair , Q1034 and Q1036 . Through R1029 , positive feedback
4-35

Tektronix FG 5010 Specifications

General

Brand	Tektronix
Model	FG 5010
Category	Portable Generator
Language	English