A need came up recently in conjunction with the restoration of an antique electronic computer that uses some odd logic levels for a circuit that would translate from 0 V/+5 V logic to 0 V/–5 V logic. In other words, when the input is at 0 V, the output should be at 0 V, and when the input is at +5 V, the output should be at –5 V. The circuit in Figure 1 was proposed. Let’s dig into its operation in detail.
What are the input characteristics of the circuit? In other words, what sort of load does the driving circuit see?