Patent GB-1449000-A (GB)
Title: Bistable multivibrator circuit
IPC: H03K3/289
Filed: 1973-12-12
Abstract: 1449000 Transistor bi-stable circuits MOTOROLA Inc 12 Dec 1973 57613/73 Heading H3T A bi-stable multivibrator includes a first section having first and second transistors 44, 46, a second section having third, fourth, fifth and sixth transistors 24A, 24B, 18 and 22, a current steering gate having a first portion 36, 38 providing a first output to the first and second transistors 44, 46 and a second portion 32A, 32B providing first and second outputs to the third and sixth transistors 24A, 22 and to the fourth and fifth transistors 24B, 18 respectively, first and second current sources 34B and 34A connected to the gate 32A, 32B, 38 and 36, a first feedback transistor 14 connected to the control electrodes of the third and fourth transistors 24A, 24B and controlled by the fifth transistor 18 and a second feedback transistor 50 connected to the control electrode of the first transistor 44 and controlled by the second and sixth transistors 46 and 22. The circuit shown can take any one of four stable states. With the clock pulse input 31 low the current steering transistors 32A, 32B are off and 36, 38 are on. This turns off the transistors 24A, 24B, 18 and 22 and allows one of the transistors of each pair 54, 20 and 46, 44 to conduct under control of the input logic signal at 55 in relation to a reference voltage source 70. When the input 55 is low the transistor 54 and 44 are off and the transistors 20 and 46 are on making the output 60 low. If now the input 55 is made high the transistors 54 and 46 turn on and the transistors 20 and 44 turn off making the output 60 low. A low input 55 causes the transistors 54 and 46 to turn off and turns on the transistors 20 and 44 to make the output 60 high. If now the input 55 is made high the transistors 54 and 44 turn on and the transistors 20 and 46 turn off to make the output 60 high. If for each input and output state above the clock pulse input 31 is changed from low to high then the current steering transistors 32A, 32B turn on and the current steering transistors 36, 38 turn off and this turns off the transistors 54, 20, 46 and 44. When both the input and output are low and the clock pulse input 31 is changed to high the transistors 18 and 22 turn on and the transistors 22, 24A are off so that the output remains at low. If when the input is high and the output is low the clock pulse input 31 is changed to high the transistors 18, 22 turn off and the transistors 24A, 24B turn on to make the output change to high. When the input is low and the output is high and the clock pulse input 31 is changed to high the transistors 18, 22 turn on and the transis - tors 24A, 24B turn off to make the output change to low. When both the input and output are high and the clock pulse input is changed to high the transistors 18, 22 are on and the transistors 24A, 24B are off to make the output. remain at high. The bi-stable circuit can be in integrated circuit form. In a modification (Fig. 2, not shown) an inverse output is provided from an additional transistor (56). In a further embodiment the input 55 and transistors 20, 54 and 38 are removed and the circuit operates as a divide by two frequency divider or toggle flip-flop. In a modification of this (Fig. 4, not shown) the transistors 44 and 46 are each replaced with a pair of transistors (44A, 44B and 46A, 46B) to provide an inverted output (67).