High Current Bandgap Voltage Regulator with Op-Amp Buffering
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Solution Overview
Problem
Existing voltage reference generation circuits are unable to provide a large current while maintaining accurate output voltage, making them inadequate for applications requiring high current sourcing.
Innovation Solution
A high current drive bandgap based voltage regulator is designed, featuring a high current drive output transistor and an operational amplifier in a feedback loop, with a feedback network that includes resistors and diodes to provide a stable reference voltage, capable of sourcing at least 100 μA of current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If existing voltage reference generation circuits are used, then the circuit structure is simple, but the current sourcing capability is insufficient and cannot provide large current while maintaining accurate output voltage
Solution Approach 1:
The voltage reference generation circuit is divided into two independent parts: a low-current accurate voltage reference generation circuit and a high-current drive output stage. The operational amplifier buffers the reference voltage and drives the output transistor separately, allowing each part to optimize its function without interfering with the other's performance characteristics.
Solution Approach 2:
An operational amplifier is introduced as an intermediary between the voltage reference generation circuit and the high-current output transistor. The op-amp receives the accurate low-current reference voltage, amplifies it through its high-gain feedback mechanism, and drives the output transistor to deliver high current while maintaining the accuracy of the original reference voltage through negative feedback.
2Quantity of substance
If high current is sourced from the output, then the current drive capability is improved, but the output voltage stability and noise performance deteriorate
Solution Approach 1:
A negative feedback loop is implemented using the operational amplifier, which continuously monitors the output voltage and adjusts the drive signal to the output transistor to maintain the desired output voltage level. This feedback mechanism ensures that even under high current load conditions, the output voltage remains stable and accurate by compensating for any deviations caused by load variations or transistor non-linearities.
3Quantity of substance
If the output transistor is designed for high current drive, then the current sourcing capability is improved, but the power supply rejection ratio worsens and noise increases
Solution Approach 1:
The circuit separates the sensitive voltage reference generation stage from the noisy high-current drive stage. The voltage reference generation circuit operates at low current with excellent power supply rejection, while the output transistor handles high current delivery. The operational amplifier acts as a buffer between these two stages, preventing noise and disturbances from the high-current stage from affecting the sensitive reference generation stage.
Data Source
AI summary
A high current drive bandgap based voltage regulator for providing a reference voltage at a an output voltage at a designed output voltage value. The high current drive bandgap based voltage regulator includes a high current drive output transistor, a feedback network, an output terminal and an operational amplifier. The feedback network is coupled between the output of the transistor and the input of the transistor. The operational amplifier is in the feedback network and has at least two operational amplifier input terminals and an operational amplifier output terminal. The operational amplifier output terminal is coupled to the transistor input terminal, and the operational input terminals are coupled to the transistor output terminal. The output terminal of the high current drive bandgap based voltage regulator is coupled to the output of the high current drive transistor. The high current drive bandgap based voltage regulator is operable to provide a current of at least 100 μA to the output terminal while maintaining the output voltage at the output terminal at a value substantially equal to the designed output voltage value.