Abstract: An ECL circuit (30.sub.1) formed with a pair of emmitter-coupled bipolar transistors (Q1.sub.A and Q1.sub.B), a main current source (26), a resistor (R1.sub.A), and an output transistor (Q2) contains a switching stage (38) for placing the circuit in the three-state mode when the circuit is operated in the normal ECL output voltage range. The switching stage causes current exceeding that supplied by the current source to flow through the resistor. The output transistor turns off, enabling the circuit to exhibit high output impedance.

Abstract: A bipolar signal translator contains a pair of transistors (Q1 and Q2) arranged as a current mirror with their emitters coupled to a voltage supply (V.sub.EE) by way of a pair of impedance elements (R4 and R5) that improve stability. Their collectors are coupled through another pair of impedance elements (R1 and R2) to an input transistor (Q4 or Q5) and to a device circuit (D1 and D2, D3 and D4, or Q4). The collector of one of the current-mirror transistors (Q2) is coupled to the base of an output transistor (Q3) whose collector is preferably coupled through an output impedance element (R3) to a current-control transistor (Q6) that improves power utilization.

Abstract: A TTL circuit having a pair of current sources (R2/V.sub.CC and R2/V.sub.CC) and a pair of transistors (Q1 and Q2) arranged in a standard TTL input/inverting configuration has hysteresis at the input signal (V.sub.X) for providing noise protection. A hysteresis circuit (10) suitably containing another current source (R3/V.sub.CC) coupled to the base of the inverting transistor (Q2) and a rectifier (12) coupled between the collector of the inverting transistor and the current source (R1/V.sub.CC) coupled to the base of the input transistor (Q1) provides the hysteresis at the circuit switching points.