Re: Morning fun - working scope with no tubes?


Hi Robin,
You are referring to the Long Tail Pair which is an incredibly versatile circuit that has been used for over 80 years n tube circuits, transistor circuits, and integrated circuits.

Wikipedia includes the historical background of this circuit in their article on Differential Amplifiers (the Long tail Pair is a simple differential amplifier):

An explanation of how the vacuum tube Long Tail Pair works is given at

Fender (and many others) used the Long Tail Pair as a phase inverter in their guitar amplifiers:

Although the Long Tail Pair circuit was originally developed for vacuum tube amplifiers it is so general it works as well for transistors. This article describes how the transistor version works and how it is used extensively in IC OpAmps and Differential Comparators:

Dennis Tillman W7PF

-----Original Message-----
From: [] On Behalf Of Robin_Birch
Sent: Friday, September 20, 2019 3:44 PM

Designing stuff so that it was, as much as possible, independent of the particular characteristics of a given device as it aged or cane from various suppliers, was one of the great skills of tube design,.

Dennis Tillman W7PF
TekScopes Moderator

Join to automatically receive all group messages.