Amplifier with folded super-followers
AssigneeTexas Instruments Incorporated
InventorsAndrija Jezdic, John L. Wallberg, Bryan E. Bloodworth
Life of this patent
Estimating the term…
Abstract
Fixed gain amplifiers have particular use in the read channel of hard disk drives. A CMOS fixed gain amplifier 18c having a constant gain over the large dynamic range of hard disk drive applications is provided by incorporating super follower transistors M3 and M4 into the input stage of the fixed gain amplifier. The super follower transistors are folded into the output stage of the amplifier. The differential current through the degeneration resistor RE1 travels through the super follower transistors M3 and M4 and into the current mirrors I5 and I6. Thus the ac differential current goes directly to the cascoded stage, into the load resistors RL1 and RL2, and to the output load.
Claims6
A CMOS fixed gain amplifier, comprising:
- a CMOS input stage for receiving a differential voltage, the CMOS input stage including;
- a first CMOS input transistor connected in series with a first current source;
- and
- a second CMOS input transistor connected in series with a second current source;
- a CMOS output stage for transmitting a fixed voltage, the CMOS output stage including:
- a first leg having a first CMOS output transistor and a third current source connected in series;
- and
- a second leg having a second CMOS output transistor and a fourth current source connected in series;
- and
- CMOS super follower transistors for coupling the input stage to the output stage so that all of a differential current flows through the super follower transistors and into the output stage.
A CMOS fixed gain amplifier, comprising:
- a CMOS input stage for receiving a differential voltage, the CMOS input stage including;
- a first CMOS input transistor connected in series with a first current source;
- a second CMOS input transistor connected in series with a second current source;
- and
- a degeneration resistor connected between the first CMOS transistor and the second CMOS transistor;
- a CMOS output stage for transmitting a fixed voltage, the CMOS output stage including:
- a first leg having a first load resistor, a first CMOS output transistor and a third current source connected in series;
- and
- a second leg having a second load resistor, a second CMOS output transistor and a fourth current source connected in series;
- and
- CMOS super follower transistors for coupling the input stage to the output stage so that all of a differential current flows through the super follower transistors and into the output stage.
The CMOS fixed gain amplifier of claim 6 wherein the common mode feedback circuit has a first connection connected to the first load resistor and a second connection connected to the first super follower transistor;
- and
- The common mode feedback circuit has a third connection connected to the second load resistor and a fourth connection connected to the second super follower transistor.
Dependencies are inferred from the claim text.