Multistage differential amplifier with CMFB circuit
View Patent ↗The invention relates to a multistage differential amplifier having an input stage, at which a differential input voltage is present, a load connected to the input stage, a CMFB circuit and an output stage, at which an amplified differential output voltage is output. In order to improve the stability of a common-mode regulating loop, a current source is provided, which additionally feeds current into the regulating loop and thereby ensures that a control voltage for the load does not fall below a predetermined value.
1. A multistage differential amplifier comprising
an input stage
a load connected to the input stage,
a CMFB circuit;
an output stages;
a feedback loop tar setting a common-mode voltage wherein a current source is provided, which additionally feeds current into the feedback loop to prevent the load from being switched off; and
a multistage differential amplifier wherein the number of stages of the differential amplifier is even.
2. A multistage differential amplifier according to claim 1 , wherein an inverting element is provided in the feedback loop.
3. A multistage differential amplifier according to claim 2 , wherein the inverting element is connected to the CMFB circuit.
4. A multistage differential amplifier according to claim 1 , wherein an I/V converter is connected downstream of the inverting element.
5. A multistage differential amplifier according to claim 4 , the I/V converter is a transistor connected as a diode.
6. A multistage differential amplifier according to claim 2 , wherein inverting element is a PMOS transistor.
7. A multistage differential amplifier according to claim 1 , wherein the load is a current mirror.
8. A multistage differential amplifier according to claim 4 , wherein the I/V converter is connected to the load.
9. A multistage differential amplifier according to claim 1 , wherein the CMFB circuit is formed as an integrated circuit.
10. A multistage differential amplifier according to claim 1 , wherein an output of the input stage is connected to a control input of the output stage.
11. A multistage differential amplifier according to claim 1 , wherein the number of stages of the differential amplifier is two.
12. A multistage differential amplifier comprising
an input stage
a load connected to the input stage,
a CMFB circuit;
an output stage;
a feedback loop for setting a common-mode voltage wherein a current source is provided, which additionally feeds current into the feedback loop to prevent the load from being switched off; and
a multistage differential amplifier wherein an inverting element is provided in the feedback loop,
wherein the current source is arranged in parallel with the inverting element.