Push-Pull MOSFET High-Voltage Amplifier for Wide Bandwidth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current amplifiers are limited in output voltage amplitude range and bandwidth, failing to meet high voltage and wide bandwidth requirements for applications such as Fringe Image Telescopy, which necessitates a solution that can achieve outputs up to 5 kV with a bandwidth from DC to 10 MHz.
Innovation Solution
A high voltage amplifier design utilizing a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) in a push-pull configuration, driven by low impedance gate drive circuits and coupled with a linear analog optocoupler, enabling a high voltage output with a bandwidth from DC to several megahertz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional tubes or transistors in series are used, then output voltage can be increased, but bandwidth is limited to 200 kHz
Solution Approach 1:
The amplifier output stage is segmented into multiple MOSFETs (first MOSFET and second MOSFET) operating in parallel rather than series, allowing high voltage output through complementary push-pull operation while maintaining wide bandwidth capability. Each MOSFET handles half the voltage swing, enabling 10 kV output without the bandwidth limitations of series configurations.
Solution Approach 2:
The invention changes the operating parameters by using MOSFETs with optimized gate drive circuits that provide sufficient driving capability for high frequency operation. The gate drive circuits are designed with low impedance to enable fast switching at high frequencies while maintaining 10 kV output voltage capability, resolving the trade-off between voltage and bandwidth.
2Stress or pressure
If high voltage output of 10 kV is achieved, then voltage amplitude range is improved, but device complexity increases
Solution Approach 1:
The first and second MOSFETs serve multiple functions: they provide the high voltage output capability, act as the power switching elements, and their complementary operation inherently provides push-pull amplification. The gate drive circuits simultaneously provide voltage boosting and signal conditioning, reducing the need for separate voltage multiplication stages and simplifying the overall structure despite the 10 kV output requirement.
3Speed
If MOSFETs are driven at high frequency, then bandwidth is increased, but cross-conduction may occur
Solution Approach 1:
The gate drive circuits are designed to turn off one MOSFET before the other turns on during the transition period. The complementary symmetry operation ensures that the gate voltages are controlled to create a dead time interval, preventing both MOSFETs from being conductive simultaneously. This preliminary timing control maintains wide bandwidth while preventing cross-conduction at high frequencies.
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 effectively achieves a high voltage output of up to 10 kV with a wide bandwidth, preventing cross-conduction and ensuring sufficient driving of MOSFETs for high frequency operation, thereby addressing the limitations of existing amplifiers.
Implementation Method 1
a first optocoupler coupled to the second low impedance gate drive circuit
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A high voltage amplifier (100) and a method of assembling and of operating a high voltage amplifier (100) are described. The device includes a first metal-oxide-semiconductor field-effect transistor, MOSFET (150b), driven by a first gate drive circuit (130b). The device also includes a second MOSFET (150a) driven by a second gate drive circuit (130a) and a first optocoupler (120) coupled to the second gate drive circuit (130a). The first MOSFET (150b) and the second MOSFET (150a) of the high voltage amplifier (100) drive a first output voltage (Vo).