The Tektronix Type 1A7 is a high-sensitivity differential plug-in for 500-series scopes. It senses down to 10 μV/Div, either AC or DC-coupled. It's possible to apply up to ± 300 mV offset to the reading while maintaining sensitivity. Upper and lower cutoff frequency is selectable on the front panel. Maximum bandwidth is 500 kHz, and common-mode rejection is 50,000 to 1.
Type 1A7's front end is a matched quad of 7586 nuvistors, with two in parallel - to reduce noise - on each input. These tubes are in temperature-equalizing housings, and mounted on a rubber-isolated subchassis. The "coarse" balance adjustment controls the relative heater voltages on the 7586's.
In 1968, the 1A7 was superseded by the FET-equipped Type 1A7A (designed by Thor Hallen), which also doubled common-mode rejection and bandwidth (to 1 MHz).
The 1A7A's differential amplifier design was re-used with some modifications in the 3A9, 3A10, 7A22, 5A22N and 5030/5031 scopes. The AM502 and 26A2 use BJTs instead of JFETs for the offset current sources.
Type 1A7A remained available until the end of the 500-series line.
|Deflection||10 μV/Div to 10 V/Div in 1–2–5 sequence|
|Input impedance||1 MΩ // 47 pF (either input)|
|— 1A7 —|
|Bandwidth||1 MHz, LF limit switchable DC, 0.1 Hz to 10 kHz in ×10 steps, HF limit switchable 100 Hz to 100 kHz in ×3/×10 steps, and 500 kHz; AC coupling 1.6 Hz|
|— 1A7A —|
|Bandwidth||1 MHz, LF limit switchable DC, 0.1 Hz to 10 kHz in ×10 steps, HF limit switchable 100 Hz to 1 MHz in ×3/×10 steps, AC coupling 1.6 Hz|
|Range||Differential signal||DC Offset||Common mode|
|10 μV/Div to 10 mV/Div||±0.4 V||±0.4 V||±10 V|
|20 mV/Div to 0.1 V/Div||±4 V||±4 V||±100 V|
|0.2 V/Div to 1 V/Div||±40 V||±40 V||±500 V|
|2 V/Div to 10 V/Div||±400 V||±400 V||±500 V|