Voltage-to-Current Converter Temperature Compensation
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Solution Overview
Problem
Conventional Voltage-to-Current converters are temperature sensitive, leading to output current drift and instability in applications like Phase-Locked-Loops and other circuits that require precise current control.
Innovation Solution
A Voltage-to-Current converter with a temperature compensation circuit, utilizing a current mirror and resistors to ensure output current independence from temperature variations, and incorporating a reference voltage to stabilize the current signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional Voltage-to-Current converter is used, then the circuit is simple and easy to manufacture, but the output current drifts with temperature changes
Solution Approach 1:
The converter circuit is divided into two symmetric branches: a signal processing branch (transistor 202 with input voltage VC) and a reference branch (transistor 210 with reference voltage VREF). Each branch has its own resistor (204 and 212 respectively), creating segmented current paths that can be independently controlled to achieve temperature compensation.
Solution Approach 2:
The invention changes the operating parameters by applying different voltages (VC and VREF) to the gates of transistors in the two branches. By controlling the reference voltage VREF, the reference current IC2 can be adjusted to compensate for temperature-induced changes in the signal current IC, thereby stabilizing the output current IC1 against temperature variations.
2Reliability
If temperature compensation is added to the Voltage-to-Current converter, then output current stability improves, but the circuit complexity increases
Solution Approach 1:
While the circuit uses symmetric structures (two transistors, two resistors), it introduces asymmetry in the control voltages applied to each branch. The signal branch receives VC and the reference branch receives VREF, allowing independent control of each current path. This asymmetric control within a symmetric structure enables temperature compensation without requiring completely different circuit topologies.
Solution Approach 2:
The reference branch serves multiple functions: it generates a temperature-compensated reference current IC2, provides a stable reference for comparison, and enables the overall temperature compensation mechanism. The current mirror transistors (206 and 208) universally copy currents from one branch to another, providing a versatile mechanism for both signal transmission and temperature compensation.
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 provides a temperature-insensitive output current, reducing drift and improving stability in applications, and is also insensitive to transistor process variations, enhancing overall performance.
Implementation Method 1
a current mirror having first and second poles, a first transistor coupled between the first pole of the current mirror and a low voltage through a first resistor, a second transistor coupled between the second pole of the current mirror and a low voltage through a second resistor
Data Source
AI summary
A Voltage-to-Current converter includes a current mirror having first and second poles, a first transistor coupled between the first pole of the current mirror and a low voltage through a first resistor, a second transistor coupled between the second pole of the current mirror and a low voltage through a second resistor wherein the second resistor is substantially identical with the first resistor, and wherein the output current is dependent on resistance of the first resistor, the input voltage signal applied to the gate of the first transistor, and a reference voltage signal applied to the gate of the second resistor.