US 4,855,622 A · TTL compatible switching circuit having controlled ramp output

Abstract

A TTL compatible buffer circuit responsive to an input signal and having a controlled ramp output is disclosed and includes a low and a high output voltage driver, each driver being comprised of a Darlington pair of transistors, and each driver being separately controlled by its own control circuit. Each control circuit includes at least a capacitor and resistor which are arranged to control the voltage at the base of the upper transistor of the Darlington pair output voltage driver. In this manner, the voltage at the high voltage driver increases in a substantially linear manner when the input signal goes from low to high, and the voltage at the low voltage driver decreases in a substantially linear manner when the input signal goes from high to low. The turn on time of the drivers is thus relatively long. Each control circuit further includes a transistor which permits the respective output voltage driver to turn off quickly. With a quick turn off and a long turn on, a break before make condition is established and voltage supply line bounce due to a feedthrough circuit is eliminated. Voltage supply line bounce due to current flow between the load capacitance at the buffer circuit output and a low voltage source through the low voltage driver upon the turning on of the low voltage driver is also substantially reduced.

Claims18

Dependent claims

A buffer circuit responsive to an input signal and for providing an output signal at an output thereof, the circuit comprising:

(a) a low voltage driver means coupled to a low voltage source and to said output of said buffer circuit;
(b) a high voltage driver means coupled to a high voltage source and to said output of said buffer circuit;
(c) driver control means for turning said low voltage driver means off before said high voltage driver means turns on when the voltage level of the input signal goes from a first level to a second level, and for turning said high voltage driver means off before said low voltage driver means turns on when the voltage level of the input signal goes from said second level to said first level;
and
(d) current limiting means for controllably limiting current flow between said output of said buffer circuit and said low voltage source through said low voltage driver means when said low voltage driver means turns on.

2 more elements

A buffer circuit responsive to an input signal and having a controlled ramp output comprising:

(a) a low voltage driver means coupled to a low voltage source and to said output of said buffer circuit;
(b) a high voltage driver means coupled to a high voltage source and to said output of said buffer circuit;
and
(c) driver control means for turning said low voltage driver means off before said high voltage driver means turns on when the voltage level of the input signal goes from a low level to a high level, and for turning said high voltage driver means off before said low voltage driver means turns on when the voltage level of the input signal goes from a high level to a low level,
said driver control means further for controlling the voltage at the emitter of said high voltage driver means and at the collector of said low voltage driver means such that when the voltage level of the input signal goes from a low level to a high level, the voltage at the emitter of said high voltage driver means increases in a controlled manner from a relatively low output level to a relatively high output level, and when said voltage level of the input signal goes from a high level to a low level, the voltage at the collector of said low voltage driver means decreases in a controlled manner from a relatively high output level to a relatively low output level.

2 more elements

Dependencies are inferred from the claim text.

TTL compatible switching circuit having controlled ramp output

Life of this patent

TTL compatible switching circuit having controlled ramp output

Life of this patent

Abstract

Claims18