282: Difference between revisions
Jump to navigation
Jump to search
No edit summary |
No edit summary |
||
| Line 2: | Line 2: | ||
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 | The high-impedance input stage is a dual-JFET where transistor A operates as a source-follower | ||
and | and transistor B operates as a current source biased with Vgs=0, maintaining a constant | ||
current through transistor A, independent of input signal voltage. | |||
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)] | ||
Revision as of 13:43, 12 December 2010
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 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 transistor A operates as a source-follower and transistor B operates as a current source biased with Vgs=0, maintaining a constant current through transistor A, independent of input signal voltage. The risetime is 3ns when driven from a 25-ohm source.