Tektronix TYPE CA Instruction Manual page 11

A PLIFIERS
The Type CA Plug-In Unit consists of two
identical amplifier channels and a channel ­
switching multivibrator. The following descrip ­
tion of the amplifiers applies equally well to
either channel.
Input Coupling and
The signal to be displayed is applied to the
input cathode follower V3323 (V4323) by way
of the AC-DC switch and the VOLT /CM switch.
The AC-DC switch is a two-position slide
switch that bypasses C3300
DC position so the input is de coupled. In
the AC position of this switch the signal must
pass through C3300 (C4300) so the d c com ­
ponent of the signal is blocked.
The VOLT /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 follower
V3323 (V4323) and the cathode-coupled phase
inverters V3334 and V3354 (V4334 and V4354).
The control-grid d c level of V3334 (V4334)
is established by the d c connection to the cathode
of V3323 (V4323). The control-grid d c level
of V3354 (V4354) is adjustable by means of the
DC BAL controls so that the d c level of the
cathodes of V3334 and V3354 (V4334 and V4354)
can be made equal. Any d c level difference
between these two cathodes would act as a signal
and cause the trace to shift position when
VARIABLE control is rotated. The VARIABLE
gain control establishes the amount
AA
Attenuation
(C4300) in the
the
of cathode
Circuit Description - Type CA
DESCRIPTION
coupling and thus allows the stage gain to be
varied over about a 2 1/2 to 1 range.
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 POLARITY switch in the NORMAL
position the displayed waveform will have the
same polarity as the input signal.
POLARITY switch in the INVERTED
reverses the signal-grid connection
and V3374 (V4364 and V4374) and
displayed waveform. Rotation of the VERTICAL
PO ITION control forces one plate
stage toward a higher potential and the
plate toward a lower potential. The
de level shift moves the trace vertically.
Amplifier Stage and Output
The signal is further amplified
and V3374 or V4364 and V4374,
which channel is conducting. V3364 and V4364
have a common plate load and likewise V3374
and V4374. ince one amplifier is always cut
off while the other is conducting,
loading effect is negligible.
V4383 is the output cathode
provides a low-impedance source
the oscilloscope's vertical amplifier.
Pos. Range control located in the
of the output cathode followers permits the trace
to be centered vertically under no-signal
ditions.
SWITCHING CIRCUIT
A ONLY , B ONLY
V3375 is a multivibrator that is
ON 3
CIRCUIT
Placing the
position
of V3364
inverts the
of the input
opposite
resulting
CF
by V3364
depending on
the shunt
follower that
for driving
The Vert.
grid circuit
con ­
controlled
3-1