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Tektronix 3A1S
25 MHz vertical amplifier
3A1S front view

Compatible with 560-series scopes

Produced from 1961 to (?)

Manuals – Specifications – Links – Pictures

The Tektronix 3A1S is a vertical plug-in for the 561S.


Deflection from 10 mV/Div to 10 V/Div (in a 561S)
Bandwidth 25 MHz
Rise time 14 ns
Input impedance 1 MΩ // 47 pF


The input signal passes through a compensated attenuator switch and then into a 7586 cathode-follower biased with 2 mA plate current.

The gain stages use a mix of transistors and output stage driving the deflection plates is a transistor/pentode cascode circuit with T-coil loading.

The 3A1S is built in traditional ceramic-strip construction.