# Gate voltage range - Biasing circuit

I am looking for Biasing circuits which can provide gate voltage in the range of -4V to -0.5V.

In the application note of AMPLEON AN-11130, there is a table mentioning the specifications of the circuit.

It is mentioned that "gate voltage adjustment" range is 700mV typical. As per note1, "Resistor values may have to be changed for part of range."

In the "6.4 Gate voltage adjustment" by adjusting resistor values of R13 and R14 the gate voltage can be trimmed.

Is it possible to get my gate voltage requirements by using this circuit?

Edit:- Added schematic snapshot Is it possible to meet my requirements by changing the resistor values of R13 and R14?

Edit 2:-

"R21 determines the supply voltage at which operating VGS is applied" What is the meaning of this? I know that these resitors are being used for setting threshold voltage for the "FB" pin. When there is transition from low to high on FB pin thresold voltages, PGOOD generates high signal. How this will control VGS generation?

• If you want to know how to modify the circuit, then you must show the circuit in the question. And tell us which part of the circuit you do not understand.
– CL.
Nov 2 '20 at 10:33
• @CL. I have added snap shot! Nov 2 '20 at 11:23

When Q2 is on, the output is always −4 V. When Q2 is off, the output is determined by the R13/R5/R14 voltage divider. With the values shown, the voltage can be adjusted between about −1.6 V and −2.4 V.

To allow voltages down to −4 V, drop R13. To allow voltages up to −0.5 V, make R14 one seventh of R5. The wiper of the potentiometer is unlikely to go all the way to the ends, so you will probably not reach these limits.

• I have edited my question Nov 3 '20 at 4:04
• "To allow voltages down to −4 V, drop R13. To allow voltages up to −0.5 V, make R14 one-seventh of R3" you meant R13 right? Nov 3 '20 at 4:34
• Sorry; I meant R5.
– CL.
Nov 3 '20 at 5:13
• What is the importance of the formulas mentioned on the "6.5. Resistort value selection" ? Nov 3 '20 at 5:22
• Those do not affect the gate voltage.
– CL.
Nov 3 '20 at 6:11