From TekWiki
Jump to navigation Jump to search
Tektronix 1A2
50 MHz dual channel amplifier
1A2 front view

Compatible with 500-series scopes

Produced from 1964 to 1975

Manuals – Specifications – Links – Pictures

The Tektronix 1A2 is a two-channel plug-in amplifier for 500-series scopes. It provides a −3 dB point of 50 MHz in a 544, 546, 547, or 556, and 50 mV/div sensitivity. It was designed by Larry Biggs.

The Type 1A2 was introduced in 1964 together with Types 1A1, 543B, 545B, 544, 546, and 547. It was designed to replace the venerable Type CA, while the 1A1 delivered ten times the sensitivity at a higher price and is able to lock channel 1 to Type 547's timebase A and channel 2 to timebase B. On the other hand, Type 1A2 can select which channel provides triggering when the mainframe is set to Plug-In mode, for scopes having this feature (544, 546, 547, 549, 556, late 555).

The 1A2 remained available until the 500-series scope line was discontinued.

Key Specifications

  • please add


1A1 and 1A2 share some mechanical design, but the circuits have few details in common.

Below serial number 11000, the 1A2 uses a 7586 nuvistor at the front end as a cathode follower. Above serial number 11100, the front-end uses a FET for this function. After the front-end buffer, one input of an NPN differential amplifier is driven to produce a differential current-mode signal at the collectors.

Silicon diodes form an analog multiplexer that switches between the two inputs. A cross-coupled pair of PNP transistors forms a multivibrator that generates the voltages that control the diodes that select the input channel.



Some Parts Used in the 1A2

Part Part Number(s) Class Description Used in
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