Amplifiers – With semiconductor amplifying device – Including current mirror amplifier
Patent
1990-06-11
1992-02-11
LaRoche, Eugene R.
Amplifiers
With semiconductor amplifying device
Including current mirror amplifier
323315, 3072768, H03F 126
Patent
active
050878913
ABSTRACT:
A current mirror curcuit has an actively controllable feedback element in the form of a p-channel field effect transistor (28). The p-channel transistor 28 has its gate connected to the output of a differential amplifier (12). The opamp 12 is connected to form a feedback loop within the current mirror circuit. The negative input (14) of the opamp (12) is connected to receive at node (16) the drain voltage V1 of the first transistor (24). The positive input (18) of the opamp (12) is connected to receive at node (20) the drain voltage (V2) of the second transistor (26). The purpose of the opamp 12 is to tend to equalize the drain voltages V1 and V2 of the first and second transistors 24, 26. If the drain voltage V2 of the second transistor 26 increases relative to the drain voltage V1 of the first transistor 24 the output signal Vo of the opamp 12 will be such as to reduce Vgs of the transistor 28 and hence Ids thereby to reduce the drain voltage V2 of the second transistor 26. If the drain voltage V2 of the second transistor 26 falls below the drain voltage V1 of the first transistor 24 the output signal of the opamp 12 will be such as to increase Vgs of the transistor 20, and hence Ids thereby to allow the drain voltage V2 of the second transistor 26 to rise. In this way the nodes 16 and 20 are continuously biased equal.
REFERENCES:
patent: 4937469 (1990-06-01), Larson et al.
Electronics Letters; L. Shofoi, J. E. Heasen; "Negative Current-Mirror Using n-p-n Transitors"; 5/26/77; vol. 13, No. 11, pp. 77-78.
Dinh Tan
Inmos Limited
LaRoche Eugene R.
Manzo Edward D.
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