A Differential Op-Amp Circuit Collection

In an era of discrete tube or transistor op-amp modules, any potential advantage to be gained from fully-differential circuitry was masked by primitive op-amp module performance. Fullydifferential output op-amps were abandoned in favor of single ended op-amps. Fully-differential op-amps were all but forgotten, even when IC technology was developed. The main reason appears to be the simplicity of using single ended op-amps. The number of passive components required to support a fully-differential circuit is approximately double that of a single-ended circuit. The thinking may have been “Why double the number of passive components when there is nothing to be gained?”