Amplifiers

Introduction The last of the JFET classical amplifier configuration is the common gate amplifier, analogous to the common base BJT amplifier.  As usual, we will derive the voltage gain, current gain, input resistance, and output resistance of this configuration. The Common Gate Amplifier For the common gate amplifier, the input signal is applied at the … Read more

Introduction The common drain amplifier is analogous to the common collector amplifier, and it is also called the source follower amplifier, as will become clear very soon.  As usual, we will derive the voltage gain, current gain, input resistance, and output resistance of this amplifier. The Common Drain Amplifier This is the common drain amplifier.  … Read more

Introduction Just like bipolar junction transistors, we also have three classical amplifier configurations for JFET that lay the foundation for all JFET amplifier theory.  They are the Common Source amplifier, the Common Drain amplifier, and the Common Gate amplifier.  In this chapter we’ll discuss the Common Source amplifier. JFET Particulars Let’s recall the small signal … Read more

Introduction We’ve spent quite some time on bipolar junction transistors, so you should be getting somewhat familiar with them.  For the next chapters we’re going to pull away from BJTs and instead of focus JFETs. BJTs and JFETs A lot of what we will discuss will sound familiar.  In many regards, JFETs circuits will exhibit … Read more

Introduction We’ve seen that a Common Base amplifier has a bigger bandwidth than the Common Emitter amplifier as it doesn’t suffer from the Miller Effect.  However, the low input resistance of the CB amplifier can be a problem: it can draw lots of current from the preceding stage, greatly “loading” it and altering its intended … Read more

Introduction So far, we have studied BJTs and their different configurations, isolated from any other circuitry.  We’ve learned a lot, and we’re much further along than we first started.  However, until now we haven’t given much thought as to our circuit’s frequency response, and how differently that can behave depending on our input signal’s frequency.  … Read more

Introduction The common base amplifier is probably the most confusing and difficult of the three classical configurations to understand, especially for beginners.  But with proper analysis techniques, it can be tamed. When first introduced to BJTs, we are taught “if you put more current in the base, much more current will flow through the transistor”.  … Read more

Introduction Our next classic configuration is the Common Collector, or CC amplifier.  We’ve already covered AC-coupling and biasing in the previous chapter on the CE amplifier.  The concept is the same here and won’t be detailed.  For the CC amplifier, we’ll learn how to Draw the DC and AC load lines Get the voltage and … Read more

Introduction Now that you have the basics needed to understand and analyze transistor circuits, let’s continue our study with the classical textbook configurations of BJT amplifiers.  You’ll find these in every course and textbook that deals with amplifiers, though not always with great explanations. The following circuits are textbook circuits, and while you may find … Read more