Storage time can be eliminated and propagation delay can be reduced by ensuring that transistors do not saturate in normal operation. Contemporary TTL logic families do this by placing a Schottky diode between the base and collector of each transistor that might saturate, as shown in Figure BJT-7. The resulting transistors, which do not saturate, are called Schottky-clamped transistors or Schottky transistors for short.
When forward biased, a Schottky diode's voltage drop is much less than a standard diode's, 0.25 V vs. 0.6 V. In a standard saturated transistor, the base-tocollector voltage is 0.4 V, as shown in Figure BJT-8(a). In a Schottky transistor, the Schottky diode shunts current from the base into the collector before the transistor goes into saturation, as shown in (b). Figure BJT-9 is the circuit diagram of a simple inverter using a Schottky transistor.