Simulating MOSFETS in Spice off, it has a very high resistance between drain and source. This is a very much like a mechanical switch. Vgs Ig = 0 g d s Q1 2N7000 g d s Q1 2N7000 g d s Q3 BS250 Q2 Q4 Id d s g Id Ig=0 g d Vgs s Ig = 0 Q1 2N7000 Id Q5 NFET Q6 PFET

Your description of #1 is a Low side switch, not a high-side switch. Look at Linear Tech data sheet for LT1089. It shows an NPN with collector tied to the positive rail, and the load is from emitter to ground. Have a look at the block diagram for LTC4446. How to Build an N-Channel MOSFET Switch Circuit. In this project, we will go over how to connect an N-Channel MOSFET to a circuit for it to function as an electronic switch. The type of N-Channel MOSFET we will use is the enhancement-type MOSFET, the most commonly used type of MOSFET. MOSFETs, like BJTs, can function as electronic switches. 2N7000 .SAM Rev. A1 These N -C hannel enhancement mode field effect transistors are produced using Fairchild's proprietary, high cell density, DMOS technology. These products have been designed to minimize on-state resistance while provide rugged, reliable, and fast switching performance. They can be used in most Relay driver, how it works? Generally, we think on the high side because we usually place the power switch in the power lead as in Fig 1. The same may be accomplished by locating the switch in the low side or return lead as in Fig 2. When controlling relays via logic etc. it is far easier to interface to the low-side driver. This tutorial will explore the use of a P-channel and N-channel MOSFETs as a power switch and general transistor theory. This switch will operate on the positive side of a power supply with a negative common. In this tutorial, some important concepts like the High and Low side Switching of MOSFET, need of Gate Driver circuit and driving methods of High side MOSFETs will be discussed. These concepts will crystal clear the working of MOSFET as a switch and will so justify the use