Receiver Output Signal Circuit With Backgate Bias for Wider Dynamic Range
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Solution Overview
Problem
The dynamic range of output signals from source follower circuits in radio communication receivers is limited by high threshold voltages of MOS transistors, which can be reduced by increasing transistor size, but this leads to increased parasitic capacitance and degraded frequency characteristics.
Innovation Solution
An output signal circuit using N-channel MOS transistors with a backgate bias generator that applies a common backgate bias voltage to lower the threshold voltages without increasing transistor size, preventing parasitic diode forward bias and maintaining good frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the threshold voltage Vth of the common gate transistor is lowered by increasing the transistor size, then the dynamic range of output signal is improved, but the parasitic capacitance increases and frequency characteristics are degraded
Solution Approach 1:
The patent applies backgate bias voltage to change the threshold voltage parameter of the MOS transistor without changing the physical size of the transistor. By controlling the backgate voltage, the threshold voltage can be adjusted to achieve wider dynamic range while maintaining the original transistor dimensions and parasitic capacitance characteristics, thus preserving frequency response.
Solution Approach 2:
The patent utilizes the backgate dimension of the MOS transistor, which is typically not used in conventional circuits, to control the threshold voltage. This additional control dimension allows independent adjustment of threshold voltage without affecting the main channel dimensions, thereby decoupling the trade-off between dynamic range and frequency characteristics.
2Speed
If the threshold voltage Vth is high, then the transistor size can be kept small and frequency characteristics are maintained, but the signal level range that brings the transistor into conduction becomes narrow
Solution Approach 1:
By applying backgate bias voltage, the patent changes the threshold voltage parameter to achieve optimal conduction characteristics. This allows the transistor to operate over a wider signal level range while maintaining small physical dimensions and good frequency characteristics.
3Power
If a source follower circuit with low output impedance is used to drive low impedance load, then the output capability is improved, but the high threshold voltage of MOS transistors limits the dynamic range
Solution Approach 1:
The patent modifies the threshold voltage parameter of the MOS transistors in the source follower circuit through backgate biasing. This enables the circuit to maintain low output impedance for driving capacitive loads while simultaneously achieving wider dynamic range by optimizing the conduction characteristics of the transistors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution increases the dynamic range of output signals while preserving frequency characteristics, even under varying temperatures, by adjusting the backgate bias voltage to avoid parasitic diode activation and reducing threshold voltages without enlarging the transistors.
Implementation Method 1
a backgate bias generator produces a backgate bias voltage Vb which is commonly applied to backgates of the transistors 1 and 2
Data Source
AI summary
According to one embodiment, an output signal circuit for use in a receiver is provided. The output signal circuit is provided with first and second transistors of an insulated gate field effect type, and a backgate bias generator. A source of the first transistor is capable of receiving an input signal. A source of the second transistor is capable of generating an output signal. A backgate bias generator produces a backgate bias voltage which is applied to backgate of the first and second transistors commonly.