282: Difference between revisions
No edit summary |
No edit summary |
||
| Line 9: | Line 9: | ||
greater than unity, which allows the overall gain of the 282 to be trimmed for exactly unity | greater than unity, which allows the overall gain of the 282 to be trimmed for exactly unity | ||
gain. The rise time is 3 ns when driven from a 25 Ω source. | gain. The rise time is 3 ns when driven from a 25 Ω source. | ||
Power supply is a [[015-0073-00]]. | |||
==Manual== | ==Manual== | ||
Revision as of 12:59, 21 January 2019
The Tektronix Type 282 is an active adapter introduced in 1966 that allows high-impedance probes to be used with instruments that have 50 Ω inputs. It is a unity-gain buffer with an input impedance of 1 MΩ in parallel with 16.5 pF and a low output impedance.
The high-impedance input stage is a dual-JFET where transistor A operates as a source-follower and transistor B operates as a current source biased with Vgs = 0, maintaining a constant (Idss) current through transistor A, independent of input signal voltage. After the FET input stage, the signal is fed to a Sziklai pair formed of a PNP transistor first, driving an NPN output transistor. The Sziklai pair is non-inverting and has a voltage gain greater than unity, which allows the overall gain of the 282 to be trimmed for exactly unity gain. The rise time is 3 ns when driven from a 25 Ω source.
Power supply is a 015-0073-00.
