Automatic Gain Control Circuit With Temperature-Canceling Detection Paths
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Solution Overview
Problem
The automatic gain control circuits in semiconductor integrated circuits exhibit temperature dependence in their gain control signals and output amplitudes due to differences in temperature sensitivity between peak and average voltage detection components, leading to unstable output amplitudes.
Innovation Solution
An automatic gain control circuit design that includes a peak detection circuit, an average value detection and output amplitude setting circuit, and a high gain amplifier, where the number of base-emitter junctions in the peak detection and average value detection paths are equal, and the resistors are made from the same material to minimize temperature dependence, ensuring the gain control signal is independent of base-emitter voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peak detection and average value detection circuits are used with different temperature sensitivities, then the gain control signal can be generated, but the output amplitude becomes unstable due to temperature dependence
Solution Approach 1:
The patent changes the parameter of transistor configuration by making the number of base-emitter junctions equal in both detection paths. This parameter change ensures that temperature-induced voltage variations affect both paths equally, thereby canceling out temperature dependence in the gain control signal and stabilizing the output amplitude across different temperatures.
2Reliability
If separate peak detection and average value detection circuits are used, then the gain control function is achieved, but the circuit complexity and chip area increase
Solution Approach 1:
The patent merges the peak detection and average value detection circuits into a unified structure where both functions share common components and transistor paths. By integrating these detection functions and ensuring equal base-emitter junction counts, the patent reduces circuit complexity and chip area while maintaining accurate gain control capability.
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
This design significantly reduces temperature dependence of the output amplitude of the variable gain circuit, maintaining a stable output amplitude across varying temperatures, while also reducing the number of elements, chip area, and power consumption.
Implementation Method 1
a peak detection circuit which detects and outputs a peak voltage of an output signal from a variable gain circuit which amplifies a main signal, and includes transistors
Implementation Method 2
an average value detection and output amplitude setting circuit which detects an average value voltage of an output signal from the variable gain circuit
Implementation Method 3
a high gain amplifier which controls a gain of the variable gain circuit by amplifying a difference between an output voltage of the peak detection circuit and an output voltage of the average value detection/output amplitude setting circuit
Data Source
AI summary
In an automatic gain control circuit, a peak detection circuit detects and outputs the peak voltage of an output signal from a variable gain circuit. An average value detection/output amplitude setting circuit detects the average value voltage of an output signal from the variable gain circuit, and outputs a calculated voltage. An amplification circuit controls the gain of the variable gain circuit by amplifying the difference between the output voltages of the peak detection circuit and average value detection/output amplitude setting circuit. The number of base-emitter junctions of transistors on a path in the peak detection circuit from input ports which receive output signals from the variable gain circuit to an output port which outputs a voltage to the amplification circuit is equal to the number of base-emitter junctions of transistors on a path in the average value detection/output amplitude setting circuit.