3A8
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
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Front, no plugin covers
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Front view, w/shield covers
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3A8 Left side
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3A8 Right side
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 |