A junction-transistor scaling circuit with 2 microsec resolution

When junction transistors are used in conventional scaling circuits the maximum speed of operation is limited by the associated circuit, mainly owing to the use of capacitors, which require time to charge and discharge. The limiting speed of a transistor itself, which depends on the switch-on and switch-off times of current, is generally several times higher than this, but cannot be taken advantage of owing to the associated circuit. The basic binary scaling circuit described in the paper overcomes this difficulty by dispensing with capacitors, a differentiating transformer being used instead for coupling. In this way the speed of the circuit depends only on transistor characteristics. With currently-available low-frequency junction transistors (fco¿¿500 kc/s) the circuit is capable of reliably resolving 2 microsec. The basic binary scaler is readily adapted to the formation of a scale-of-5 circuit using three binary stages. When this is preceded by another binary scaler, the result is a scale-of-10 circuit with the same resolving capabilities as the original binary circuit. The circuits have wide tolerances and are insensitive to transistor variations. A complete scale-of-10 circuit uses eight transistors, ten diodes and five transformers.