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Tektronix Type Z
Comparator preamp plug-in
Type Z front view

Compatible with 500-series scopes

Produced from 1960 to 1969

Manuals – Specifications – Links – Pictures

The Tektronix Type Z is a comparator plug-in for 500-series scopes, introduced in 1960 and dropped after 1968.

The Type Z has two inputs, A and B, plus a precision comparison voltage, VC, that is adjustable from 0 to ±1 V, 10 V, or 100 V via a ten-turn pot.

The following differential amplifier can be configured to display VA, −VB, VA−VB, VA−VC, or VC−VB.

This allows DC-coupled measurements of small signals with large DC offsets.

Unlike later comparators, Type Z has separate step attenuators for each input, permitting the user to view the difference between signals of widely differing amplitudes. Unfortunately the divider resistors have no trim, so CMRR is poor except at 50mV/div.

It is also the only comparator that can handle ±100 V common mode at full sensitivity.

With a pair of "Disconnect Signal" buttons, the Type Z was the first movement toward a "GND" position on the input switches.

The Type P6023 probe with R and C compensation, introduced in 1962, was specifically designed for the Type Z but also marketed for the Type G.


Maximum sensitivity is 50 mV/div, and common-mode rejection is 40,000:1 "from DC through audio frequencies".

Risetime as a general-purpose amplifier is 27 ns (13 MHz bandwidth). A side effect of Type Z's unprecedented dynamic range is that transient response is a function of signal amplitude: slew rates faster than 1V in 6ns will cause distortion due to grid current.


The Type Z uses both tubes and transistors, capitalizing on the strengths of each.

The step attenuators are turret attenuators.


  • $525 in 1962 ($4,750 in 2021 dollars)




Some Parts Used in the Z

Page Class Description Used in
12AT7 Vacuum Tube (Dual Triode) dual high-gain triode 161 180 310 310A 315 316 360 502 502A 512 513 513D 514 514AD 514D 516 524AD 529 RM529 544 546 547 556 3A2 3A75 1M1 A B C G H K L M N K R S Z
12AU6 Vacuum Tube (Pentode) RF pentode 81 112 512 556 575 545 549 581 585 A B C G K H L M N O R S Z
6AK5 Vacuum Tube (Pentode) RF pentode B C CA G K L S Z 517 517A
6DJ8 Vacuum Tube (Dual Triode) dual triode 80 132 161 310A 316 317 3A75 502 502A 503 504 515 516 519 526 529 RM529 533 535 536 543 544 545 545A 545B 546 547 549 555 556 565 581 581A 585 585A 661 2A60 63 2A63 3A7 3A8 1121 1A4 67 81 82 86 3B1 3B4 1S1 B O W Z Telequipment S32A Telequipment D52 Telequipment TD51 Telequipment S52 Telequipment S51 Telequipment Type A