MOS Transconductance Amplifier with Wide Tuning and Linear Input Range
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Solution Overview
Problem
Conventional transconductance amplifiers experience a narrowing of the operating input range and loss of linearity between input voltage and output current when tuning the transconductance, limiting the range in which output current is proportional to input voltage.
Innovation Solution
A transconductance amplifier design that maintains linearity by controlling both the tuning voltage and common voltage, with a constant ratio between them, allowing for broader tuning of transconductance while ensuring the linearity between input voltage and output current over the predetermined operating input range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the tuning voltage Vctrl is varied to tune transconductance, then the transconductance Gm can be adjusted, but the linearity between input voltage and output current deteriorates and the operating input range is narrowed
Solution Approach 1:
The patent changes the operating region parameter of the MOS transistors from saturation region to triode region. By operating the differential pair transistors in triode region instead of saturation region, the patent achieves both wide transconductance tuning range and maintained linearity between input voltage and output current, resolving the technical contradiction.
2Adaptability or versatility
If the tuning voltage Vctrl is increased to expand transconductance tuning range, then broader tuning is achieved, but the constant transconductance range is diminished and linearity is lost
Solution Approach 1:
The patent changes the operating region parameter of the MOS transistors from saturation region to triode region. This parameter change enables the differential pair to operate linearly across a wider input voltage range while allowing broad transconductance tuning, thus expanding the operating input range while maintaining ease of operation.
3Reliability
If the MOS transistors are operated in saturation region, then high gain is achieved, but the linearity between input voltage and output current is poor and tuning range is limited
Solution Approach 1:
The patent changes the operating region parameter of the MOS transistors from saturation region to triode region. This fundamental parameter change enables simultaneous achievement of high linearity between input voltage and output current and wide transconductance tuning range, resolving the contradiction between reliability and adaptability.
Data Source
AI summary
An embodiment of the present invention has a differential pair including a first and second MOS transistors having their sources grounded; a third and fourth transistor with their source terminals connected to drain terminals of the first and second transistors, respectively; a voltage generating circuit for outputting tuning and common voltage so that the ratio between the common and tuning voltage is constant; and a differential pair input voltage generating circuit that receives the input and common voltage to output voltages Vip and Vin to gate terminals of the first and second transistors, respectively. The gate terminal of the fourth transistor is connected to the gate terminal of the third transistor, and the tuning voltage is input to the two terminals.