Maximum and Minimum Qpoint Values Design the circuit below s

Maximum and Minimum Q-point Values

Design the circuit below such that I_DQ = 0.25mA and V_DQ = -2V.
Given V_TP = -1.2V, K_P = 0.25 mA/V², Assume ? = 0.

Determine the maximum and minimum Q-point values if the tolerance of the K_p parameter is ±10%.

Solution

IDQ = 0.25mA

and VDQ = -2V.
Given VTP = -1.2V,

KP = 0.25 mA/V2,

Assume = 0.

IG = 0, we can apply voltage divider to the gate: VG= RG2/(RG1+RG2) VDD = 5 V Because VG > Vt the transistor is on Assume saturation region, solve the problem, and then verify Notice that: VS = (ID )(RS ) = 6 ID (ID in mA) Then: VGS = VG – VS = 5 V – 6 ID ID = ( ½ kn’)(W/L)( VGS – Vt ) 2 = ( 1/2 mA/V2 )(5 V – 6 ID – 1V ) 2 18 ID 2 - 25 ID + 8 = 0 Solving for ID we obtain: ID = 0.89 mA and ID = 0.5 mA