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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. It was designed by Charlie Rhodes and Ron Olson.

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 (~$5,300 in 2023 dollars)





Some Parts Used in the Z

Part Part Number(s) Class Description Used in
0G3 154-0291-00 Gas Discharge Tube (Voltage regulator) 85 V voltage reference 132 506 547 560 561 561A 561S 564 565 567 661 TU-4 Z
12AT7 154-0039-00 Vacuum Tube (Dual Triode) dual high-gain triode 161 180 310 310A 315 316 360 502 502A 511A 512 513 513D 514 514AD 514D 516 524 529 RM529 544 546 547 556 565 570 3A2 75 3A75 1M1 A B C G H K L ML M N K R S Z
12AU6 154-0040-00 Vacuum Tube (Pentode) RF pentode 81 112 1L10 1L20 1L60 3L10 512 556 575 545 547 549 581 585 A B C G K H L ML M N O R S Z
6AK5 154-0014-00 154-0206-00 154-0084-00 Vacuum Tube (Pentode) RF pentode B C CA G K L ML S Z 517 517A 524
6DJ8 154-0187-00 154-0305-00 Vacuum Tube (Dual Triode) dual triode 132 161 310A 316 317 502 502A 503 504 506 515 516 519 526 529 RM529 533 535 536 543 544 545 545A 545B 546 547 549 555 556 561A 561S 564 565 567 581 581A 585 585A 661 1A4 1S1 60 2A60 63 2A63 67 2B67 3A1 3A1S 3A2 3A3 3A6 3A7 72 3A72 75 3A75 4S2 51 3B1 3B1S 3B2 3B3 3B4 3M1 3S76 3T77 3T77A 9A1 9A2 1121 80 81 82 86 B O W Z Telequipment D56 Telequipment S32A Telequipment D52 S-311 Telequipment TD51 Telequipment S52 Telequipment S51 Telequipment Type A TU-4
RT5204 151-0058-00 Discrete component Silicon NPN transistor 565 RM565 Z 2A61 3B1 3B3 3S76 3T77