Vdsat Mosfet

## 7.4. Overview¶

A thorough treatment of MOSFETs can be found in Chapter 4 of the ELEC 2210 textbook,Microelectronics Circuit Design by R.C. Jaeger.

### 7.4.1. Transistor Characteristics¶

In this lab, we will first measure the I-V characteristics of MOSFETs,including: Question: For A N-MOSFET With The Following Process Parameters VTO=0.5V, KP=50uA/V^2, W=2um, L=1um. (a) Using Spice, Simulate IDS Versus VDS Curves For VGS=0 To 5V In 0.5V Step. VDS Range Is From 0 To 5V, In Step Of 0.01v. Identify The (Vdsat, Idsat) Point On Each Curve With A Marker (you Can Do This By Hand On Printed Plots). Example: Analysis of DC bias circuit for a MOSFET transistor. Ment mode MOSFET, one that is only “on” with a channel present when the magnitude of the gate voltage exceeds a critical value known as the threshold voltage. 2.2 The n-channel silicon MOSFET. Left: The circuit schematic of an enhancement mode MOSFET showing the. 1. Ids-Vgs in a saturation byconnection configuration, e.g.with gate tied to the drain, from which we candetermine threshold voltage.
2. Ids-Vds curves for multiple gate-to-source voltages (Vgs), from whichwe can observe linear and saturation operation regions.

## Mosfet Vdsat Calculation

Using measured threshold voltage and Ids-Vds curves, we can thencheck how well first-order MOSFET theory holds up in real devices andget a practical feel of the limitation of first-order theoretical MOSFETequation.

The MOSFETs we will use in this experiment are from ALD1105, an ICcontaining two n-MOSFETs and two p-MOSFETs.A circuit symbol description of the two pairs of transistorsfrom the data sheet is shown below in figure 1.

Figure 1: Circuit Symbol and Pin Numbers for the Pairs of N-channel and P-channel MOSFETs. Note each transistor has four terminals: drain (D), source (S), gate (G), and substrate, which iscalled body (B) in our text.As we learned in class, all the n-MOSFETs on an IC share the same p-type body, whichneeds to be tied to the lowest voltage in a system to keep all the source/drain to body PN junctions zero or reverse biased.

Similarly, all the p-MOSFETs on an IC share the same n-type body, which needs tobe tied to the highest voltage in a system to keep all the source/drain to body PN junctionszero or reverse biased.

The pin diagram seen in figure 2 shows the package layout and various pin connections for ALD1105.

## Mosfet Vdsat Equation

### 7.4.2. CMOS Inverter¶

MOSFETs are mostly used in CMOS circuits.There are many advantages of CMOS, with the biggest beingzero standby power consumption, at least ideally.

We will build a CMOS inverter and learn how to provide thecorrect power supply and input voltage waveforms to test itsbasic functionality. For a given supply VDD, your voltage low shouldbe zero, and voltage high should be VDD.

By default, the function generator gives an output that variesfrom -VPP/2 to +VPP/2, with VPP being peak-to-peak voltage.For a square wave, the voltage low is -VPP/2, voltage high is+VPP/2. You can set the DC offset to VPP/2 to make voltage low 0.

We will build complexCMOS logic gates and sequential CMOS circuits from scratch usingtransistors in other labs.