C Ir C U It D E S C R Ip T Io N - Tektronix TYPE L Instruction Manual

General
The Type L Plug-In
pream plifier incorporating a fast-rise high-
gain ac am plifier and a fast-rise dc amplifier.
Maximum ac sensitivity
centim eter, and maximum dc sensitivity is 0.05
volt per centimeter.
The main am plifier of the Type L Unit
consists of a Phase
produces X2 amplification, preceded and fo l­
lowed by cathode followers. When the AC-DC
switch is in X10 GAIN
am plifier is placed in cascade with the main
am plifier of the unit.
Input Circuit
Either ac- o r dc-coupling from the signal
source may be selected with the AC-DC switch,
SW5002. In DC position, the signal is coupled
straight through to the VOLTS/CM switch.
In AC or X10 GAIN
to the VOLTS/CM switch through a blocking
capacitor, C5002, which removes the dc com­
ponent. In addition, the X10 GAIN AC position
switches the X10 am plifier into the circuit
and increases and decouples the voltage on
the screen of the Input Cathode Follower.
The VOLTS/CM switch, SW5052, inserts f r e ­
quency-compensated attenuators into the input
circuit. The nine-step
voltage-attenuation
10 X, 20 X, 40 X, 100 X, 200 X,
produce deflection factors of .005, .01, .02,
.05, .1, .2, .5, 1, and 2 volts per centimeter
in X10 GAIN AC and .05, .1, .2, .5 ,1 ,2 ,
5, 10 and 20 volts
o r DC. When the attenuators are properly
adjusted, the effective resistance and capaci­
tance at the INPUT connector remain unchanged
as the attenuators are switched in the circuit.
AA
Unit is a fast-rise
is 0.005 volt per
Inverter Stage which
AC position, a X10
AC the signal passes
attenuator has
ratios of IX , 2X , 4X,
and 400 X, to
per centimeter in AC
Circuit Description - Type L Plug-In
D E S C R I P T I O N
The attenuators are frequency-compensated
voltage dividers. At low
capacitors have a high impedance and their
effect in the circuit is negligible--the atten­
uators act as resistive dividers with the atten­
uation being proportional to the ratio of the
resistances. As the frequency of the input
signal is increased, however, the impedance
of the capacitors decreases and their effect in
the circuit becomes more pronounced. F or high-
frequency signals, the impedance of the capaci­
tors is low in comparison to the resistance of
the circuit, and the attenuators become capaci­
tive voltage dividers. F or these frequencies, the
degree of attenuation is inversely proportional
to the ratio of the capacitances. A variable
capacitor in each attenuator provides a method
fo r adjusting the capacitance.
Each attenuator network
capacitor for adjusting the input capacitance
to a standard value of 20 pf at the INPUT
connector for all positions of the VOLTS/CM
switch. C5732 in the grid circuit of V5832
is used to standardize the unit with the X I
network switched into the circuit. The trim m er
capacitor at the input of each of the other
attenuator networks adjusts the input capacitance
o f the attenuator to the standard value.
Frequency compensation of each attenuator
network is provided by the trim m er capacitor
near the attenuator output.
Input Cathode Follower
The F irst Cathode Follow er, V5832 provides
isolation between the input circuitry and the
amplification circuits. It prevents changes in
the am plifier from changing the input charac­
teristics of the plug-in, and it prevents changes
in the source or attenuator switching from
affecting the operation of the amplifiers.
C I R C U I T
frequencies, the
has a variable
3-1