Small Signal And Large Signal Anaysis In Electronics?

Posted on 09 February 2010

2 Comments For This Post

1. Have a scientastic day! says:
   February 9th, 2010 at 9:18 pm

   sorry, can’t provide you with a voltage or current range because it totally depends on the device you are using.
   Small signal analysis is used for signals that are small enough to be within the linear range of the device being used. This linear range varies from device-to-device.

2. Chuck says:
   February 9th, 2010 at 9:18 pm

   I can’t give you a specific voltage or current range because that depends on the devices you are using.
   But the principle is that small signal analysis makes the assumption that the parameters that characterize a device (such as the forward current transfer ratio of a bipolar transistor) can be considered to be constant over the current range of the signal. This means that the device behaves approximately as a linear device over this range. Also, the device is usually biased to have a quiescent current and voltage that is more or less in the middle of the range of output swings that will be experienced. Sometimes the term “Class A” is used to describe this application.
   Large signal applications (typically power amplifiers) have large excursions of current & voltage such that the device parameters can no longer be approximated with constant values. In these applications, the device will exhibit significant non-linear behavior such that linearized analysis will not be adequate. Sometimes power amplifiers are used in a “push-pull” arrangement where one transistor will carry the positive signal excursions and another will carry the negative excursions – Termed “class-B” since current does not flow continuously in this application. The extreme of non-linear operation is when the devices are used as switches – either on or off, and not much time spent in between.

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