Section _ Understanding (Darlington transistor ) or Darlington pair

Examining  ( Compound Supply) Bias Divider Voltage  in  Darlington Transistor  =  Pair or Even

  Researcher  and author: Dr.   (   Afshin Rashid)



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Note: However, in the self-powered method, the Rs resistor creates negative feedback to some extent, stabilizing the bias divider voltage of  the Darlington transistor.

 If we want the circuit to have the highest stability point, we use a circuit according to the bias divider voltage. In this circuit, the voltage divider bias R1 and R2 and the  self-supply circuit (resistor RS) are used simultaneously. For this reason, this supply is also called a compound supply. Given that   no current flows through the gate of the Darlington transistor pair,  the emitter voltage is equal to the potential drop across the resistor R2, in  other words, VDD is divided between R1 and R2 and VG  is obtained from DD. Since this voltage  is positive, in order for VGS to become negative, the collector potential, i.e.  RSID, must be greater than VG so that the gate-emitter and collector junction  arebias of the Darlington transistor pair . 

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The resistive voltage in  the Darlington transistor pair  can also be obtained by using a transfer curve such as the bias plot analysis in the operating characteristic through the resistive voltage. In this plot, the load line on the VGS characteristic curve is not zero because the  bias type resistors create a potential drop in the base or emitter at the voltage point. Therefore, in the divider of this circuit, the DC load line passes through the origin of the coordinates, that is, from a point in the DC voltage loop in the  Darlington transistor pair or pair  . The input to the circuit is not the  DC voltage in the Darlington transistor pair or pair .



To create a suitable operating point, we must  bias  the  Darlington pair as we would a BJT. The methods of biasing a Darlington pair  are not fundamentally different from those of biasing a BJT; it should only be noted that because the input resistance  of the Darlington pair  is very high, very little current  (about a few nanoamperes or picoamperes) flows through the gate, which can be ignored. In the calculations, IG is taken equal to zero. This simplifies the calculations. The simplest method of biasing a Darlington pair  is to use two separate voltage sources for (emitter and collector). This method is called biasing with constant supply voltages.

  •   Researcher  and author: Dr.   (   Afshin Rashid)

  • Specialized PhD in Nano-Microelectronics