The Tektronix Type W is a differential comparator plug-in amplifier for 500-series scopes. Its bandwidth varies from 23 MHz to 8 MHz depending on gain. Only modestly faster than its Type Z predecessor, Type W extends performance in terms of sensitivity, reaching 1 mV/div, and achieves 20,000 to 1 common-mode rejection at DC and low frequencies.
Type W has two signal inputs, "A" and "B", and a built in precision variable voltage supply, "VC", which is controlled by a ten-turn pot and can vary from either −1.1 V to +1.1 V or −11 V to +11 V. A mode switch selects between displaying A−VC, A−B, or VC−B. The "A−B" mode is particularly useful for displaying the current in a sense resistor, while the other modes provide "slideback" measurements of small variations superimposed on a large constant. An output of VC is provided on the front panel for precision measurements.
Unlike the Type Z, Type W has two gain axes, a decade attenuator and a 1−2−5−10−20−50 selector, reminiscent of Type D from ten years before.
Type W is the only letter-series plug-in with an "infinite resistance" input mode selectable at the front panel. (Type 1A5 has an internal jumper that can be cut.)