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The '''Tektronix Type 282''' is an active adapter [[introduced in 1966]] that allows high-impedance | {{Instrument Sidebar | ||
probes to be used with instruments that have 50 Ω inputs. It is a unity-gain buffer | |manufacturer=Tektronix | ||
|model=282 | |||
|class=Amplifier | |||
|series= | |||
|summary=Unity gain buffer | |||
|image=Tek 282 1.jpg | |||
|caption=Tektronix Type 282 | |||
|introduced=1966 | |||
|discontinued=(?) | |||
|designers= | |||
|manuals= | |||
* [[Media:070-0544-00.pdf|Tektronix 282 Manual (PDF)]] | |||
}} | |||
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 withan 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 | 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 V<sub>gs</sub> = 0, maintaining a constant (I<sub>dss</sub>) 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. | ||
and transistor B operates as a current source biased with V<sub>gs</sub> = 0, maintaining a constant (I<sub>dss</sub>) 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. | |||
This active adapter is powered over [[1S1]], [[3S1]] and [[3S76]]. | This active adapter is powered over [[1S1]], [[3S1]] and [[3S76]]. | ||
==Pictures== | ==Pictures== | ||
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</gallery> | </gallery> | ||
[[Category:Oscilloscope probe accessories | [[Category:Oscilloscope probe accessories]] | ||
[[Category:GR874]] | [[Category:GR874]] | ||
Revision as of 08:18, 19 August 2021
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 withan 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.
This active adapter is powered over 1S1, 3S1 and 3S76.
