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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 with
|manufacturer=Tektronix
an input impedance of 1 MΩ in parallel with 16.5 pF and a low output impedance.
|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.   


The high-impedance input stage is a dual-JFET where transistor A operates as a source-follower
It is a unity-gain buffer withan input impedance of 1 MΩ in parallel with 16.5 pF and a low output impedance.  
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]].
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.


==Manual==
==Power Supply==
* [http://w140.com/tek_282.pdf Tektronix 282 Manual (PDF)]
The 282 internally is supplied with ±10 V stabilized with Zener diodes. This allows the 282 to be compatible with the different negative supply voltages being present on the B pin of the [[Probe_power|probe power connector]] ranging from -12.2 V (3S1) to -25 V (4S1).
===Compatible probe power=== 
* [[1S1]]
* [[3S1]]
* [[3S76]]
* [[4S1]]
* [[4S2]]


==Pictures==
==Pictures==
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Tek 282 5.jpg
Tek 282 5.jpg
Tek 282 6.jpg
Tek 282 6.jpg
282 in 1970 Catalog.jpg | 282 in 1970 catalog
Tek 282.jpg
Tek 282.jpg
Tek 282.gif
Tek 282.gif
</gallery>
</gallery>


[[Category:Oscilloscope Probe Accessories]]
[[Category:Oscilloscope probe accessories]]  
[[Category:Introduced in 1966]]
[[Category:GR874]]
[[Category:GR874]]

Revision as of 02:16, 31 October 2021

Tektronix 282
Unity gain buffer
Tektronix Type 282

Produced from 1966 to (?)

Manuals
(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

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.

Power Supply

The 282 internally is supplied with ±10 V stabilized with Zener diodes. This allows the 282 to be compatible with the different negative supply voltages being present on the B pin of the probe power connector ranging from -12.2 V (3S1) to -25 V (4S1).

Compatible probe power

Pictures