Current source circuit diagram of the operational amplifier and Darlington transistors

The Darlington transistor circuit BSY86 produces a large output current, with a maximum limit of 150 ohms. The output current is adjustable via resistor R and the RP1 potentiometer, maintaining constancy regardless of the load resistance Rl. The potentiometer RP1, rated at 10k ohms, allows current adjustments in the range of 5µA to 40mA. Additionally, the circuit features three inputs (A, B, C) that can replace the potentiometer RP1. The emitter potential of the BSY86 can be adjusted to ground using RP2 to -0.6V, while the sliding contact of the potentiometer regulates the positive terminal potential to -12V, allowing for the cancellation of resistance R and potentiometer RP1.

The described circuit employs a Darlington transistor configuration utilizing the BSY86 transistor to achieve high current gain. The output current is effectively managed through a combination of fixed and variable resistances, enabling fine control over the output characteristics. The adjustable resistor R, coupled with the RP1 potentiometer, provides a means to set the desired output current level, which is crucial in applications requiring precise current control.

The use of a 10k ohm potentiometer (RP1) is significant as it allows for a broad range of current adjustments, from a minimal 5µA to a maximum of 40mA. This flexibility is particularly useful in circuits where load conditions may change, ensuring that the output current remains stable and within specified limits. The incorporation of three inputs (A, B, C) further enhances the circuit's versatility, permitting alternative configurations depending on the application's requirements.

The adjustment of the emitter potential to ground through RP2 to -0.6V is a critical feature, as it establishes a reference point for the operation of the Darlington pair. This configuration can improve the linearity and response of the circuit, especially in applications involving signal amplification or current regulation. Furthermore, the ability to set the positive terminal potential to -12V enables the circuit to operate within a defined voltage range, optimizing performance while minimizing the risk of component stress.

Overall, this circuit design illustrates the effective use of a Darlington transistor in conjunction with adjustable resistive components to achieve a stable and controllable output current, suitable for various electronic applications.As a result of the Darlington transistor circuit BSY86 the output current is large. Output current 150 ohms maximum limit, the output current is adjusted by the resistor R by t he RP1 potentiometer, and maintained constant independent of the load resistance Rl. FIG potentiometer RP1 using 10k Europe, the current can be adjusted within the range of 5uA ~ 40mA. Op amp inputs A, B, C three partially available instead of confining potentiometer RP1, then the emitter potential BSY86 can be adjusted to the ground by RP2 -0.6V, the sliding contact of the potentiometer regulator positive terminal potential to -12V, then the resistance R and potentiometer RP1 can be canceled.