Two stage current mirror
First Claim
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1. A current mirror, comprising:
- (a) a first stage comprising a reference current input for receiving a reference current,a first bipolar transistor coupled to the reference current input and having an emitter current representative of the reference current;
voltage generating means for generating a voltage proportional to a current, said voltage generating means coupled to the emitter of the first bipolar transistor for generating a voltage proportional to the emitter current of the first bipolar transistor;
a second bipolar transistor coupled to the first bipolar transistor and to the output of the first stage for generating at the emitter of the second bipolar transistor a controlled voltage representative of the reference current;
(b) a second stage with a second stage input coupled to the output of the first stage, said second stage comprising one or more output field effect transistors (FETs) with their gates coupled to the controlled voltage for generating second stage output currents in the output FETs proportional to the controlled voltage of the first stage output and representative of the reference input current.
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Abstract
An A-to-D converter 300 has a comparator 126 with a number of comparator cells 902. Each comparator cell 902 includes a current mirror 1700 that reduces kickback noise. Current mirror 1700 includes a bipolar current mirror 1705 and an NMOS current mirror 1709. The bipolar current mirror 1705 provides an ac ground paralleling NMOS transistor 1704 in the NMOS current mirror 1709 to reduce kickback noise.
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Citations
23 Claims
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1. A current mirror, comprising:
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(a) a first stage comprising a reference current input for receiving a reference current, a first bipolar transistor coupled to the reference current input and having an emitter current representative of the reference current; voltage generating means for generating a voltage proportional to a current, said voltage generating means coupled to the emitter of the first bipolar transistor for generating a voltage proportional to the emitter current of the first bipolar transistor; a second bipolar transistor coupled to the first bipolar transistor and to the output of the first stage for generating at the emitter of the second bipolar transistor a controlled voltage representative of the reference current; (b) a second stage with a second stage input coupled to the output of the first stage, said second stage comprising one or more output field effect transistors (FETs) with their gates coupled to the controlled voltage for generating second stage output currents in the output FETs proportional to the controlled voltage of the first stage output and representative of the reference input current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of mirroring currents, comprising the steps of:
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providing first and second stages in a current mirror, said first stage comprising first and second bipolar transistors; providing an input reference current to the collector of the first bipolar transistor; generating a voltage at the emitter of the first transistor representative of the input reference current; generating a controlled output voltage at the emitter of the second bipolar transistor representative of the input reference current; connecting gates of one or more output FETs to the controlled voltage to provide one or more output currents representative of the input reference current. - View Dependent Claims (20, 21, 22, 23)
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Specification