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US 4,777,451 AGranted
Differential circuit
AssigneeFujitsu Limited
InventorKay Tohyama
Life of this patent
Estimating the term…
Abstract
To increase a voltage gain of a differential circuit, constant current source type FETs in which a source and a gate are short circuited are used as a load element and as a current source. A constant voltage type FET is used as a clamp to clamp the load element. Therefore, a temperature characteristic and a deterioration of an AC characteristic, which cause problems in a conventional diode clamp type differential circuit, can be improved.
Claims7
A differential circuit, coupled to a low voltage power source and a high voltage power source, comprising:
- a first drive FET and a second drive FET each having a gate connected to an input, having a drain, and having a source, the sources of said first drive FET and said second drive FET being commonly connected at a node;
- a constant current FET connected between the node and the low voltage power source;
- a first load circuit provided between the drain of said first drive FET and the high voltage power source;
- a second load circuit provided between the drain of said second drive FET and the high voltage power source;
- each of said first and second load circuits being formed by a first load FET having a drain connected to the high voltage power source, and having a gate and a source which are short-circuited and connected to the drain of the corresponding one of said first and second drive FETs, and a second load FET having a drain connected to the high voltage power source, having a source connected to the dran of the corresponding one of said first and second drive FETs and having a gate with a constant voltage applied thereto;
- and
- output terminals connected to the drains of said first drive FET and said second drive FET, respectively.
4 more elements
An integrated circuit device comprising:
- a high voltage power source;
- a low voltage power source;
- an intermediate voltage power source between said high voltage power source and said low voltage power source;
- input terminals;
- a converter circuit coupled to said input terminals, including:
- first and second drive FETs, each having a gate connected to a corresponding one of said input terminals, having a drain and having a source, the sources of said first drive FET and said second drive FET being commonly connected at a node;
- a constant current FET connected between the node and said low voltage power source;
- a first load circuit provided between the drain of said first drive FET and said high voltage power source;
- a second load circuit provided between the drain of said second drive FET and said high voltage power source;
- each of said first and second load circuits being formed by a first load FET having a drain connected to said high voltage power source, and having a gate and a source which are short-circuited and connected to the drain of the corresponding one of said first and second drive FETs, and a second load FET having a drain connected to said high voltage power source, having a source connected to the drain of the corresponding one of said first and second drive FETs and having a gate with said intermediate voltage applied thereto;
- output terminals connected to the drains of said first drive FET and said second drive FET;
- an internal circuit provided between said high voltage power source and said intermediate voltage power source and having a third load FET and a third drive FET in series, and of said output terminals of said converter circuit being connected to the gate of said third drive FET in said internal circuit.
9 more elements
Dependencies are inferred from the claim text.