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Tektronix Type D
Differential amplifier
D front view

Compatible with 500-series scopes

Produced from 1954 to 1969

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

The Tektronix Type D is a differential amplifier plug-in for 500-series scopes. It was designed by Rodgers Jenkins.

Type D was the most sensitive plug-in of the original four. The bandwidth depends on the gain, ranging from 2 MHz at 50 mV/div to 300 kHz at 1 mV/div. There are two axes of sensitivity setting: a decade attenuator in front of a gain switch. This scheme would be reprised in Type W.

It displays the difference between two input signals, with a common-mode rejection ratio of 10,000. It has six tubes, on a shock-mounted subchassis to avoid microphonics.

Along with Types A, B, and C, Type D was introduced with the 531 and 535 in 1954.

At the time it was called Type 53D. It was briefly renamed 53D/54D in 1955 with the introduction of the 541 and 545. This quickly changed to 53/54D, and finally shortened to just "D" in 1959 with the introduction of the 5xxA scopes. Its final year in the catalog was 1968; it had been superseded by Type 1A7 and 1A6.

K, L, and T are tied for longest production life, at 16 years. B, D, and G are next at 15 years.

Lavoie Laboratories produced an unauthorized clone, the Lavoie LA-265-D.


Instruments below serial number 3462 used a pair of 5814 tubes at the input; later production used 12AU7's. These two tube types have different heater currents, and because the heaters are series-wired, you cannot switch from one type to the other without circuit modification.

Key Specifications

Deflection 1 mV/Div to 50 V/Div in 1–2–5-10-20-50 sequence and 1-10-100-1000 sequence
Input impedance 1 MΩ // 47 pF (either input)
Bandwidth 2 MHz with MV/CM MULTIPLIER set to 50; 300kHz with MV/CM MULTIPLIER set to 1
CMRR 10000:1 with MILLIVOLTS/CM set to 1, 1000:1 otherwise
Signal ranges
Range Common mode dynamic range*
MILLIVOLTS/CM = 100 ±250 V
MILLIVOLTS/CM = 1000 ±500 V
  • In practice, Type D behaves well up to about +/–15V if the CM signal is either a brief excursion or a constant. If the CM varies slowly, DC shift in the input tubes will degrade CMRR.


Some Parts Used in the D

Page Class Description Used in
12AU7 Vacuum Tube (Dual Triode) dual medium-μ triode 104 104A 122 160 161 162 181 190 310 316 317 502 502A 511A 512 516 517 517A 524 526 535 536 545 545A 545B 547 549 555 575 581 581A 585 585A C D E N Q
5814 Vacuum Tube (Double Triode) twin medium-μ triode D
5879 Vacuum Tube (Pentode) sharp-cutoff pentode 112 512 D E