3A8

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Tektronix 3A8
Operational amplifier plug-in
3A8 Front View

Compatible with 560-series scopes

Produced from 1965 to 1972

Manuals
(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

The Tektronix 3A8 is an operational amplifier plug-in for 560-series scopes, designed by Roy Hayes and introduced in 1965. The 3A8 contains two operational amplifiers and a vertical display amplifier.

Each operational amplifier has external inputs and outputs. Input and feedback resistances / capacitances are separately switch-selectable to provide a variety of operational amplifier functions. External components can be substituted by way of front panel banana jacks, which also accept special purpose modules (see Accessories, below.)

The display amplifier can be connected to the output of either operational amplifier, or an external input. The input can be AC or DC coupled and can be inverted.

Key Specifications

 Gain Bandwidth Product ≥10 MHz
 DC Open Loop Gain ≥10,000
 Output ≥±25 V driving ≥7.5 mA (including feedback current)
Display Amplifier Bandwidth DC to 3.5 MHz
Display Amplifier Sensitivity 20 mV/cm to 10 V/cm, 1−2−5

Internals

The 3A8 has several transistors plus three 9-pin vacuum tubes, an 8416 and two 6KV8s.

Each operational amplifier has a number of transistors plus three Nuvistors: a 6CW4 and a selected pair of 7586s.

Accessories

013-0048-01 Terminal Adapter Assembly (empty box for user chosen components)
013-0049-01 Standard Shielded Cover (two supplied with each plugin)
013-0067-00 Logarithmic Amplifier Adapter
013-0068-00 Gating Adapter
013-0081-00 Compensating Adapter
013-0086-00 Leakage Current Adapter

Calibration Fixtures

067-0507-00 Grid Current Checker

Pictures

Components

Some Parts Used in the 3A8

Part Part Number(s) Class Description Used in
6CW4 154-0323-00 Vacuum Tube (Triode) Nuvistor triode 1A7 3A8 3B2 3S76 6R1 565 S-311
6KV8 154-497 154-0497-00 Vacuum Tube (Triode/Pentode) triode-pentode combo 3A8
7586 154-0306-00 Vacuum Tube (Triode) Nuvistor triode M 1A1 1A2 1A5 10A2 10A2A 11B1 11B2A 321 321A 3A1 3A1S 3A3 3A5 3A6 3A7 3A8 3A74 3S76 3T77 3T77A 3B5 4S1 4S2 6R1 6R1A 9A1 9A2 82 86 S-311
8416 154-0413-00 157-0116-00 Vacuum Tube (Dual Triode) dual triode 1S1 2A61 3A8 3L5 W