Monday 10 January 2011
Saturday 8 January 2011
amplyfire ckt
The problem with class-B amplifier design is that we start with an output stage in two halves, each with a non-linear response, which we then add together to try to give a linear response, i.e. so that a graph of output voltage vs. input voltage is a straight line.
The term "complementary symmetry" is often mentioned in connection with class-B output stages, as if there were some advantage in symmetry. Symmetrical responses of the two halves only guarantees that when added together the resulting non-linearity is all symmetrical.
To achieve a linear response what we need are two non-linear responses which add up to give a straight line. The simple solution to this problem is to start with a single half of the output stage with a conventional non-linear response, and then subtract this response from a straight line to give the response needed for the other half the output stage.
To achieve this we can start with the well known circuit shown next:
Fig. 1
This circuit gives an output acros its load equal to the difference between its inputs. This arrangement, with the addition of a power transistor, is then used as the top half of the class-B circuit shown next:
The term "complementary symmetry" is often mentioned in connection with class-B output stages, as if there were some advantage in symmetry. Symmetrical responses of the two halves only guarantees that when added together the resulting non-linearity is all symmetrical.
To achieve a linear response what we need are two non-linear responses which add up to give a straight line. The simple solution to this problem is to start with a single half of the output stage with a conventional non-linear response, and then subtract this response from a straight line to give the response needed for the other half the output stage.
To achieve this we can start with the well known circuit shown next:
Fig. 1
Fig. 2
Friday 7 January 2011
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