PMOS Transistor Circuit - Is It Enhancement or Depletion Mode?

[opticaltempest]

Here is the problem:

The PMOS transistor in the figure is conducting current.
(a) Is V_TP > 0 or V_TP < 0 for this transistor?
(b) Based on the value of V_TP, what type of transistor is in the circuit?
(c) Is the proper symbol used in this circuit for this transistor?
(d) If the symbol is not the correct one, which one should be used?


Here is the circuit:

http://img72.imageshack.us/img72/946/circuitri9.jpg


Here are the transistor symbols from which we must choose:

http://img410.imageshack.us/img410/972/symbolsyf0.jpg


Here are equations corresponding to PMOS transistors:

http://img299.imageshack.us/img299/4448/equationskg7.jpg


I'm a little confused as to how I can determine whether V_TP is greater or less than zero. I think it is going to depend on the values of the resistors. Is it possible to work through this problem mathematically in order to verify this?

Thanks

 

[hxtasy]

I would think you could formulate all the answers just from looking at the specs you provided for the transistor. What answers have you came up with so far?

 

[piercas]

for your question. I would approach this problem by first understanding the basics of PMOS transistors. PMOS transistors are a type of metal-oxide-semiconductor field-effect transistor (MOSFET) in which the majority charge carriers are holes. They have three terminals - source, drain, and gate - and can operate in either enhancement mode or depletion mode.

(a) In order to determine whether V_TP is greater or less than zero, we need to understand how PMOS transistors work. In enhancement mode, the transistor is off when the gate-to-source voltage (V_GS) is zero, and turns on as V_GS becomes more negative. In depletion mode, the transistor is on when V_GS is zero, and turns off as V_GS becomes more negative. In this case, since the transistor is conducting current, we can infer that V_GS is negative. Therefore, V_TP must be less than zero for this transistor.

(b) Based on the value of V_TP, we can determine that the transistor in this circuit is operating in depletion mode. This is because V_TP is negative, indicating that the transistor is on when V_GS is zero.

(c) The symbol used in the circuit for the PMOS transistor is not the correct one. The symbol used is for an enhancement mode PMOS transistor, which has a positive V_TP. A depletion mode PMOS transistor should have a negative V_TP, as seen in the proper symbol in the image provided.

(d) The correct symbol for the PMOS transistor in this circuit should be the one with a negative V_TP, as shown in the image provided. This symbol accurately represents the behavior of the transistor in the circuit, which is operating in depletion mode.

In order to verify this mathematically, we can use the equations provided for PMOS transistors. By plugging in the values for V_GS and V_TP, we can determine the type of transistor and whether the symbol used is correct or not. This approach would also allow us to calculate the values of the resistors needed to achieve the desired behavior of the transistor in the circuit.

In conclusion, the PMOS transistor in this circuit is operating in depletion mode, with a negative V_TP. The proper symbol for this transistor is the one with a negative V_TP, as shown in the image provided. By understanding the basics of PMOS transistors and using the equations provided, we