Tektronix CA PLUG-IN, Instruction Manual

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AMPLIFIERS
The Type CA Plug-In Unit consists of two
identical am plifier channels and a channel-
switching multivibrator. The follow ingdescrip-
tion of the am plifiers applies equally w ell to
either channel.
Input Coupling and Attenuation
The Signal to be displayed is applied to the
input cathode follow er V3323 (V4323) by way
o f the AC-DC switch and the VOLTS/CM switch.
The AC-DC switch is a two-position slide
switch that bypasses C3300
(C4300) in the
DC position so the input is de coupled. In
the AC position of this switch the Signal must
pass through C3300 (C4300) so the de com-
ponent of the Signal is blocked.
The VOLTS/CM switch is a 9-position rotary
switch that selects the various frequency-
compensated rc attenuator sections. The sen-
sitivity of the unit is .05 volts/cm, The input
voltage is reduced by the eight individually
selected attenuator sections to give nine fixed
calibrated ranges.
Input Stage
The input stage consists of the cathode follow er
V3323 (V4323) and the cathode-coupled phase
inverters V3334 and V3354 (V4334 and V4354).
The control-grid de level of V3334 (V4334)
is established by the de connection to the cathode
o f V3323 (V4323). The control-grid de level
o f V3354 (V4354) is adjustable by means of the
DC B A L Controls so that the de level of the
cathodes of V3334 and V3354 (V4334 and V4354)
can be made equal. Any de level difference
between these two cathodes would actasaSignal
and cause the trace to shift position when the
V AR IAB LE control is rotated. The VARIABLE
gain control establishes the amount of cathode
SECTION 3
C IR C U IT
D E S C R IP T IO N
coupling and thus allows the stage gain to be
varied over about a 2 1/2 to 1 ränge.
The GAIN ADJ control permits the basic
gain of the unit to be accurately set to agree
with the front-panel calibration.
Polarity and Positioning
With the P O L A R IT Y switch in the NORMAL
Position the displayed waveform w ill have the
same polarity as the input Signal. Placing the
P O L A R IT Y switch in the INVERTED position
reverses the signal-grid connection of V3364
and V3374 (V4364 and V4374) and inverts the
displayed waveform. Rotation of theV E R TICAL
POSITION control forces one plate of the input
stage toward a higher potential and the opposite
plate toward a lower potential. The resulting
de level shift moves the trace vertically.
Amplifier Stage and Output CF
The Signal is further amplified by V3364
and V3374 or V4364 and V4374, depending on
which channel is conducting. V3364 and V4364
have a common plate load and likewise V3374
and V4374. Since one am plifier is always cut
o ff while the other is conducting, the shunt
loading effect isnegligible.
V4383 is the output cathode follow er that
provides a low-impedance source for driving
the oscilloscope’ s vertical amplifier. TheV ert.
Pos. Range control located in the grid Circuit
o f the output cathode followers permits the trace
to be centered vertically under no-signal con-
ditions.
S W IT C H IN G C IR C U IT
A O N L Y , B O N L Y
V3375 is a multivibrator that is controlled
AA
Circuit Description - Type CA
3-1