Bias Current Circuit Using Single Control Signal Switching
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Solution Overview
Problem
The existing bias current circuit is complex due to numerous transistors and requires multiple standard voltages and control signals, leading to increased scale and power consumption, which complicates the switching between supplying and stopping the bias current.
Innovation Solution
A bias current circuit using P-type metal oxide semiconductor field effect transistors (MOSFETs) with a simple configuration that allows switching between supplying and stopping the bias current using a single control signal, where the circuit includes a current source connected to the drain and gate terminals of field-effect transistors, and switches are used to connect or disconnect the bias current based on the control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional bias current circuit using bipolar transistors and multiple MOS transistors is used to switch bias current, then the bias current can be supplied or stopped, but the circuit complexity increases due to numerous transistors and multiple control signals
Solution Approach 1:
The invention extracts and eliminates redundant transistors and control circuits from the conventional bias current circuit. By removing the complex bipolar transistor differential pairs and multiple MOS transistor switches, the design retains only the essential current mirror transistors (Q1-Q4) and a single control transistor (Q5), thereby simplifying the circuit while preserving the bias current switching function.
Solution Approach 2:
The control transistor Q5 serves multiple functions: it acts as a switch to enable/disable the bias current, and through its connection to the current mirror circuit, it simultaneously controls the current flow to multiple output channels. This multi-functional design eliminates the need for separate control circuits for each output, reducing overall circuit complexity.
2Measurement precision
If multiple standard voltages and control signals are input to numerous transistors for bias current control, then precise current control is achieved, but the number of input terminals and control requirements increases
Solution Approach 1:
The invention merges multiple control functions into a single control terminal. Instead of requiring separate control signals for each transistor or output channel, the design uses one control terminal connected to transistor Q5 that simultaneously controls the bias current for all output channels through the current mirror mechanism, thereby reducing the number of input terminals while maintaining control precision.
Solution Approach 2:
The current mirror circuit (Q1-Q4) copies the control signal from the single control transistor Q5 to multiple output channels. This copying mechanism allows one control terminal to effectively control multiple outputs with the same precision as if each had its own control terminal, eliminating the need for multiple independent control signals.
3Measurement precision
If amplifiers with high gain are connected to each magnetoresistive element to amplify minute sensor output signals, then signal amplification is achieved, but power consumption increases due to many amplifiers operating
Solution Approach 1:
The bias current circuit enables periodic operation of amplifiers by allowing the bias current to be supplied only during the reading operation and stopped during wait states. This periodic activation of amplifiers through bias current control reduces overall power consumption while maintaining signal amplification capability when needed.
Solution Approach 2:
The circuit discards the bias current (and thus amplifier operation) during periods when signal amplification is not required (wait states), and recovers it when reading operations commence. This on-demand bias current supply reduces cumulative power consumption across multiple read-wait cycles while preserving the ability to amplify signals when necessary.
Data Source
AI summary
A bias current circuit includes: an N-type MOSFET in which a gate terminal and a drain terminal are connected to a current source, and N-type MOSFETs in which respective drain terminals are connected to respective bias current output terminals and source terminals are grounded. The bias current circuit further includes: an N-type MOSFET in which one terminal type, either a drain terminal or a source terminal, is connected to the gate terminal of the N-type MOSFET, and the other terminal type is connected to the gate terminals of the N-type MOSFETs, and an N-type MOSFET in which a drain terminal is connected to the gate terminals of the N-type MOSFETs and a source terminal is grounded. A control signal, that is LOW when the bias current is supplied and is HIGH when the bias current is not supplied, is input to the gate terminal of the N-type MOSFET, and an inverse signal of the control signal is input to the gate terminal of the N-type MOSFET.