Transistor Temperature Sensor Circuit for Low Voltage Operation
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Solution Overview
Problem
Existing temperature sensors face challenges in operating at low voltages and suffer from noise interference and non-linear output voltage responses to temperature changes, making them unsuitable for modern applications requiring frequency stability and low power consumption.
Innovation Solution
A temperature-sensor circuit utilizing a transistor with a specific resistor configuration to enhance voltage sensitivity and reduce noise, allowing for adjustable output voltage and operation at low voltages, and incorporating a temperature-compensated piezoelectric oscillator to minimize noise and improve phase stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple diodes are coupled in series to increase temperature sensitivity, then voltage sensitivity with respect to temperature is improved, but power supply voltage requirement increases
Solution Approach 1:
The patent changes the fundamental parameter used for temperature sensing from diode voltage characteristics to transistor base-emitter voltage characteristics. The transistor's Vbe voltage exhibits a well-known temperature dependence (approximately -2mV/°C) that provides sufficient temperature sensitivity without requiring multiple series components, thereby resolving the contradiction between sensitivity and voltage requirement.
2Measurement precision
If a thermistor is used as a temperature-sensitive element to achieve temperature sensing, then temperature detection is enabled, but linearity of output voltage with respect to temperature deteriorates
Solution Approach 1:
The patent switches from using a thermistor (which has exponential resistance-temperature characteristics) to using a transistor's base-emitter voltage (which has approximately linear temperature dependence). This parameter change maintains temperature detection capability while significantly improving output linearity, eliminating the need for complex linearization circuits.
3Measurement precision
If an amplifier is used to amplify the output voltage of a single diode temperature sensor, then voltage sensitivity is improved, but noise from the amplifier affects the output
Solution Approach 1:
The patent changes the sensing mechanism from diode voltage to transistor base-emitter voltage, which naturally provides higher voltage sensitivity (approximately -2mV/°C) compared to diode characteristics. This intrinsic sensitivity enhancement eliminates the need for external amplification, thereby avoiding the introduction of amplifier noise while maintaining high temperature sensitivity.
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 enables a temperature-sensor circuit with high sensitivity and reduced noise, capable of operating at low voltages while maintaining high temperature sensitivity and phase noise reduction in temperature-compensated piezoelectric oscillators.
Implementation Method 1
A temperature-sensor circuit includes a transistor Tr1... a first resistor R1 having a first end and a second end, the first end being coupled with the collector... a second resistor R2 having a third end and a fourth end, the third end being coupled with the second end of the first resistor. A junction joining the first resistor and the second resistor is coupled with the base.
Data Source
AI summary
A temperature-sensor circuit includes: a transistor having an emitter that is grounded, a collector, and a base; a first resistor having a first end and a second end, the first end being coupled with the collector; and a second resistor having a third end and a fourth end, the third end being coupled with the second end of the first resistor. A junction joining the first resistor and the second resistor is coupled with the base.