### O/p resistance of Mosfet

In analog applications such as current mirrors or active loads, it is important for the transistor to have a large output resistance. Such circuits emulate a current source or current sink, and the Norton resistance of such a circuit should be large for ideal behavior.
The output resistance, usually denoted by rO, is a measure of how much drain-to-source voltage change is necessary to cause a given change in transistor output current when the transistor is in active mode. This resistance depends upon VGS, of course, because the channel conductivity depends upon the number of carriers within it, and that increases with gate voltage. However, rO also varies with VDS.
The reason a change in drain bias changes the resistance is that the channel exists only when the oxide field is sufficient to form a channel. At the source itself the oxide field is dependent upon the voltage drop VGS, which in active mode is above the threshold voltage, and so a channel forms. However, near the drain the oxide field depends upon VGD, and the applied drain voltage VDS makes VGD smaller than VGS because VDS brings the drain closer in voltage to the gate than is the source. The field in the oxide above the channel interpolates between these two values. In the ohmic or triode mode, a channel exists all the way from source to drain. But in the active mode, the drain voltage is high enough that somewhere between the source and drain the oxide field becomes too low to form a channel. The channel ends and dumps its carriers into the bulk semiconductor to finish their trip toward the drain without a channel. The termination of the channel is called the pinch-off point and it moves toward the source as the drain voltage increases. The channel becoming shorter as drain bias increases, the resistance between source and pinch-off point drops, so there results a lowering of output resistance with increase in drain bias. This phenomenon is called either channel-length modulation or the Early effect.
According to a simple empirical model patterned after the bipolar model for output resistance, the output resistance is given by:
$r_O = \left. \frac {\partial V_{DS}}{\partial I_{DS}}\right|_{V_ {GS}=\text{constant} } = \frac{ 1/\lambda + V_{DS}}{I_{DS}(V_{GS},\ V_{DS})} ,$
where λ is called the channel-length modulation parameter with dimensions V−1 and 1/λ plays the role of the Early voltage VA found in the bipolar model. The current IDS(VGS, VDS) is the drain current evaluated at the selected gate and drain voltages. It should be noted that this formula for output resistance is largely a fiction of hand analysis, and cannot be trusted. For example, the figure shows a tentative attempt to establish λ for a rather old 3/4μm technology. A single value for λ provides only a crude indicator of the slope of these curves in active mode.
To illustrate that λ is a function, not a constant, the lower figure shows measured values of VA=1/λ for a 0.18μm MOSFET process at a bias in the active mode of VGD=VGS−VDS=0 V. Here, VA = 1/λ increases by an order of magnitude as the channel becomes stronger. The need to employ a variety of λ-values is even greater in today's technology where λ is a function of device geometry in three dimensions (not just channel length, although this is important) and bias voltages. In practice, a particular value is calculated for each situation using a numerical model of the transistor or is measured directly.
Generally speaking, the output resistance of MOSFETs is low, and where high resistance is necessary, special circuit techniques involving multiple transistors are implemented to increase the effective resistance.

### Build a Low Noise And Drift Composite Amp Circuit Diagram

How to Build a Low Noise And Drift Composite Amp Circuit Diagram. This circuit offers the best of both worlds. It can be combined with a low input offset voltage and drift without degrading the overall systems dynamic performance.
Low Noise And Drift Composite Amp Circuit Diagram

Compared to a standalone FET input operational amplifier, the composite amplifier circuit exhibits a 20-fold improvement in voltage offset and drift. In this circuit arrangement, A1 is a highspeed FET input op amp with a closed-loop gain of 100 (the source impedance was arbitrarily chosen to be 100 kfl). A2 is a Super Beta bipolar input op amp. It has good dc characteristics, biFET-level input bias current, and low noise. A2 monitors the voltage at the input of A1 and injects current to Als null pins. This forces A1 to have the input properties of a bipolar amplifier while maintaining its bandwidth and low-input-bias-current noise.

### High Power Output Amplifier TDA7294

The famous SGS-THOMSON ST Microelectronics has introduced a Hi-Fi DMOS high-power amplifier circuit TDA7294, its sound great taste bile, which due to its internal circuit from input to output are field-effect devices, rounded sound Mild, delicate Rounuan.  However, with its assembly amplifier, only TDA7294 single-output power is only 70 W, BTL access law is 100 W from top to bottom, do not feel that power cushion. The author several tests, used to promote TDA7294-level, direct-drive one to four pairs of high-power transistor parallel, the output of strong currents, the power output of 400 W (mono), and the circuit is simple and no need to debug that can reliably work Basically, the IC has maintained a sound and performance.  Ruzuo The figure below shows, R6 for the feedback resistor, the author of the value in debugging 22 k Ω more appropriate, R6 also decided this circuit gain, the gain value will increase.  Quiescent current depends on the power of R7, R8, when its value…

### Full Power Mobile Phone Jammer Circuit Diagram

Full Power Mobile Phone Jammer Circuit Diagram.To day if we are talking about expert Cell phone Jammers we are conversing about this schematic underneath. First off all you should be very very cautious how to use this apparatus. Its completely illegal and so the reason. I post this Circuit is only for educational and testing causes. This type of apparatus is being utilised by security for VIPS, particularly at their limousines to avoid blasting device initiating while the vehicle passes from the goal cell phone-bomb. Off course there are those who use it to make a antic or to make the persons crazy in the rectangle block you are.
The power of the jammer is currently sufficient to do your thing, but certainly you can place a 30W linear power amp at the RF output and impede a much wider locality. So, Be pleasant individual with that and recall that there are people who may need desperately to obtain or make a call and one of them could be you! And if you can't oppose of functioning …