Figure 12-25 shows a simple operational amplifier that we can use as an example to identify and analyze the important functional components discussed in the previous section. 01 and 02 form the input differential stage. The signal inputs are shown grounded because we will presently perform a de analysis of the entire amplifier, and we wish to verify that…
Instead of using resistors in series with the collectors of Qj and Oz in a differential amplifier, many integrated-circuit designsernploy transistors to form active loads for 0\ and 02. Figure 12-23 shows a widely used configuration. He e. PN~ transistors 03 and 04 form a kind of current mirror, bu’t the current in diode-connected 03 is determined by the…
The current source in some older designs and in some discrete amplifiers is simply a voltage source connected in series with a large resistance. The Norton equivalent circuit of this arrangement shows that the constant current is EIR and that the source resistance is R. where E is the voltage source and R is the resistance in series with…
Although it is possible to obtain closely matched transistors for differential amplifiers. particularly in integrated circuits, it is not reasonable to expect that the paramcters of both devices will be exactly the same. or that they will track (change in the slime way) under variations in temperature or bias level. Differences in parameter value’ cause the amplifier to be…
One attractive feature of a differential amplifier is its ability to reject signals that arc common to both inputs. Since the outputs are amplified versions of the difference between the inputs, any voltage component that appears identically in both signal inputs will be “differenced out,” that is, will have zero level in the outputs. (We have already seen that…
Also, we have already shown that the double-ended (difference) voltage ga:n equals the transistor gain and that the singlc-enocd output gain is one-half that value. Therefore, we conclude that We should note that these gain relations are valid irrespective of the magnitudes and phase relations of the two inputs Vii and Vi~’ We have considered only the two special cases…
INTRODUCTION Differential amplifiers are widely used in linear integrated circuits. They are a fundamental component of every operational amplifier. which, as we shall learn. is an extremely versatile device with a broad range of practical applications. We will study the circuit theory of differential amplifiers in some detail, in preparation for a more comprehensive investigation of the capabilities (and…
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