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(New page: The Tektronix Type 282 is an active adapter introduced in 1966 that allows high-impedance probes to be used with instruments that have 50-ohm inputs. It is a unity-gain buffer with an...) |
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The Tektronix Type 282 is an active adapter [[introduced in 1966]] that allows high-impedance | The Tektronix Type 282 is an active adapter [[introduced in 1966]] that allows high-impedance | ||
probes to be used with instruments that have 50-ohm inputs. It is a unity-gain buffer with | probes to be used with instruments that have 50-ohm inputs. It is a unity-gain buffer with | ||
an input impedance of 1 megohm in parallel with 16.5 picofarads and a low output impedance. | an input impedance of 1 megohm in parallel with 16.5 picofarads and a low output impedance. | ||
The high-impedance input stage is a dual-JFET where one transistor operates as a source-follower | |||
and the other transistor operates as a current source biased with Vgs=0. | |||
The risetime is 3ns when driven from a 25-ohm source. | The risetime is 3ns when driven from a 25-ohm source. | ||
* [http://w140.com/tek_282.pdf Tektronix 282 Manual (PDF)] | * [http://w140.com/tek_282.pdf Tektronix 282 Manual (PDF)] | ||