Amplifier Bypass Switching to Limit MOSFET Charge Leakage
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Solution Overview
Problem
Existing amplification circuits, such as those using MOSFETs, suffer from charge leakage when switching between amplification and bypass modes, leading to increased operation time and reduced withstand voltage due to charge storage in capacitors and other elements.
Innovation Solution
An amplification circuit design that includes a filter circuit, an amplifier, a capacitor, a bypass line, and a switch circuit with FETs and resistance elements, where the switching times of the FETs are staggered to minimize charge leakage, and a control circuit manages the power level-dependent switching to optimize operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If MOSFETs are connected in multiple stages to increase withstand voltage, then the withstand voltage is improved, but the total number of MOSFETs increases and the influence of electric charges leaked from the MOSFETs becomes larger, extending the time required to complete amplification operation
Solution Approach 1:
The switch circuit is segmented into multiple FETs connected in series, where each FET handles a portion of the total voltage. This segmentation allows the circuit to achieve high withstand voltage capability while managing charge leakage effects by distributing them across multiple smaller units rather than having one large switch handle all voltage and charge simultaneously.
Solution Approach 2:
The control circuit turns off FETs in a specific sequence (first FETs closer to the input side, then FETs closer to the output side) before the amplifier needs to complete its operation. This preliminary action of staged turn-off prevents charge leakage from propagating to the amplifier, ensuring the amplifier can complete its operation without delay from accumulated charge effects.
2Device complexity
If a single MOSFET is used for switching between bypass circuit and low-noise amplifier, then the device complexity is reduced, but the MOSFET cannot withstand high voltages and the charge leakage effect is more significant
Solution Approach 1:
Instead of using one large MOSFET, the switching function is segmented across multiple smaller FETs connected in series. Each FET experiences only a fraction of the total voltage, allowing the use of smaller, more manageable components while achieving the required overall withstand voltage capability.
Solution Approach 2:
The control circuit acts as an intermediary that manages the complex switching sequence of multiple FETs, transforming the complexity of multi-FET coordination into a simple control function. This mediator approach handles the coordination complexity centrally rather than requiring complex interconnections between FETs themselves.
3Ease of operation
If MOSFETs are used in the switch circuit, then the switching operation is simple, but electric charge leaks from the MOSFET when changed from ON state to OFF state, propagating through the signal path and storing in capacitors
Solution Approach 1:
The charge leakage problem is segmented by distributing multiple FETs in series, where each FET's leakage charge is a smaller portion of the total. The control circuit segments the turn-off process into stages, turning off FETs in sequence from input side to output side, which prevents cumulative charge leakage from affecting the amplifier operation.
Solution Approach 2:
The control circuit applies preliminary anti-action by turning off FETs in a specific sequence before charge leakage can propagate to the amplifier. By first turning off FETs closer to the input side and then FETs closer to the output side, the system preemptively prevents charge leakage from reaching and affecting the amplifier operation.
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
This design reduces charge leakage, improves withstand voltage, and shortens the time required to complete amplification operations by ensuring efficient switching between bypass and amplification modes.
Implementation Method 1
When a MOSFET is in the ON state, a channel is generally formed between the drain and the source of the MOSFET and an electric charge is stored.
Implementation Method 2
When the MOSFET is changed from the ON state to the OFF state, the electric charge leaks.
Implementation Method 3
a first resistance element connected in series to a gate of the first FET, and a second resistance element connected in series to a gate of the second FET
Data Source
AI summary
An amplification circuit includes a filter circuit, an amplifier, a capacitor, a bypass line, and a switch circuit that includes a first FET and a second FET connected in series between one end and the other end of the bypass line, a first resistance element connected in series to a gate of the first FET, and a second resistance element connected in series to a gate of the second FET. A first control signal is supplied to the gate of the first FET. A second control signal is supplied to the gate of the second FET. A product of a gate length and a gate width of the first FET and a resistance value of the first resistance element is smaller than a product of a gate length and a gate width of the second FET and a resistance value of the second resistance element.