BiCMOS Mixer Driver Circuit Slew Rate Improvement
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Solution Overview
Problem
Existing CMOS FET-based mixer devices suffer from nonlinearities at higher frequencies due to gate drive signals that often operate in undesirable non-linear regions, limiting the dynamic range and linearity of the circuit.
Innovation Solution
The use of bipolar-complementary metal oxide semiconductor (BiCMOS) integrated circuit devices with a two-stage architecture, where bipolar junction transistors (BJTs) generate high slew-rate gate drive signals to improve linearity, and CMOS FETs mix these signals to produce output signals with enhanced frequency transformation capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If CMOS FET-based mixer devices use gate drive signals at higher frequencies, then frequency transformation capability is improved, but linearity deteriorates due to operation in non-linear regions
Solution Approach 1:
The mixer device is divided into two functional stages: a driver stage that generates the gate drive signal and a mixing stage that performs frequency transformation. This segmentation allows the driver stage to be optimized for signal quality (linearity) while the mixing stage is optimized for frequency conversion, resolving the contradiction between speed and manufacturing precision
Solution Approach 2:
The patent changes the key parameter of slew rate by using bipolar junction transistors instead of CMOS FETs in the driver stage. Bipolar transistors provide higher slew rates and can deliver larger amplitude signals with faster edges, enabling the gate drive signal to quickly traverse the non-linear region of the CMOS FETs, thereby maintaining linearity while achieving high-frequency operation
2Productivity
If gate drive signal amplitude is increased to improve dynamic range, then productivity is improved, but linearity deteriorates as FETs operate longer in non-linear regions
Solution Approach 1:
The driver stage is designed to produce gate drive signals with very high slew rates that quickly skip through the non-linear transition region of the CMOS FETs. By rushing through the non-linear region in a brief interval, the signal spends most of its time in linear regions, thereby maintaining linearity while enabling larger amplitude signals for improved dynamic range
3Manufacturing precision
If gate drive signal edges are made slower to maintain linearity, then manufacturing precision is improved, but speed deteriorates due to extended transition time through non-linear regions
Solution Approach 1:
The patent fundamentally changes the slew rate parameter by substituting bipolar junction transistors for CMOS FETs in the driver stage. The bipolar transistors inherently provide much faster switching speeds and higher slew rates, enabling the gate drive signal to have sharp edges that quickly traverse the non-linear region, thereby achieving both high speed and high linearity simultaneously
Data Source
AI summary
A mixer device is disclosed, which is fabricated as a bipolar-complementary metal oxide semiconductor (BiCMOS) integrated circuit device, to provide improved linearity and dynamic range, at higher operating frequencies. A mixer device configured according to an embodiment includes a driver circuit comprising bipolar junction transistors (BJTs) to convert a local oscillator signal to a high slew-rate gate drive signal. The driver circuit is configured as a quasi-complementary driver employing NPN BJTs. The mixer device further includes a mixer circuit comprising CMOS field-effect transistors (FETs) configured to mix an input signal with the gate drive signal to generate an output signal through the application of the gate drive signal to the gate port of the CMOS FETs. The mixer device further includes a voltage biasing circuit to provide a biased body voltage to the FETs to allow overdriving to a negative voltage relative to the body voltage.