Decreasing current in preload circuit

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SUMMARY

The discussion focuses on designing a preload circuit that applies 0.15A at 24V when a control signal reaches 7.5V and decreases linearly to 0A at 10V. A voltage-controlled resistor circuit using a FET is suggested as a potential solution. Additionally, a voltage-to-current converter circuit utilizing an operational amplifier (op-amp) and an NPN transistor is recommended, which should be gated by a comparator circuit that monitors the control signal voltage with hysteresis. These approaches provide effective methods for achieving the desired current control in the preload circuit.

PREREQUISITES
  • Understanding of FET (Field Effect Transistor) operation
  • Knowledge of operational amplifiers (op-amps) and their applications
  • Familiarity with comparator circuits and hysteresis
  • Basic principles of current and voltage control in electronic circuits
NEXT STEPS
  • Research voltage-controlled resistor circuits using FETs
  • Learn about designing voltage-to-current converter circuits with op-amps
  • Study comparator circuit design and implementation with hysteresis
  • Explore linear current control techniques in electronic circuits
USEFUL FOR

Electronics engineers, circuit designers, and hobbyists working on preload circuits or those interested in current control applications in electronic systems.

rrburkha
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I am working on a preload circuit and am having a difficult time with it. The objective is to apply .15A @ 24V when a control signal reaches 7.5V and decrease current in a somewhat linear fashion to 0A when the control signal reaches 10V.

I was looking into a voltage controlled resistor circuit using a FET.

Any other suggestions or help would be appreciated.
 
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rrburkha said:
I am working on a preload circuit and am having a difficult time with it. The objective is to apply .15A @ 24V when a control signal reaches 7.5V and decrease current in a somewhat linear fashion to 0A when the control signal reaches 10V.

I was looking into a voltage controlled resistor circuit using a FET.

Any other suggestions or help would be appreciated.

Sounds like you could use a voltage-to-current converter circuit with an opamp and NPN transistor. You'd gate that circuit with the output of a comparator circuit that tests the input control signal voltage against 7.5V (with a little hysteresis built into the comparator, of course).

Can you sketch something like that up?
 

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