Magnus Encyclopedia

The O page

Short for operational amplifier.

Operational Amplifier
An operational amplifier is an amplifier which has a diffrential input, an output and which has features the more or less well approximate the ideal characteristics of an operational amplifier. Among the important charachteristics is a high voltage gain, high input impedance, low output impedance, high CM suppression (high CMRR factor), high slew-rate, a high frequency cutoff, linear phase and a low noise. Of course is there no real amplifier which is at the ideal values, but the varity of opamps which exists today and their general usabillity in cursuitry has made them very popular in a wide range of products. They have become as basic building block as resistors and capacitors.

Operational Transconductance Amplifier
Operational Transconductance Amplifiers is devices which act as an operational amplifier but have an current output. Instead of raw gain (output voltage divided with input voltage) they have a transconductance (output current divided with input voltage). It is common that this transconductance can be changed over a large range (1:1000000 is not uncommon) by an extrernal voltage or current. This property have made OTAs usfull in VCAs, VCFs VCOs and numerous other applications. Some OTAs will also come with a builtin voltage buffer at the output, this is paricularly usefull in some cursuits. An OTA will act as an 2-quadrant multiplier.

See Operational Transconductance Amplifier

(C) 1997, 1998, 1999
Magnus Danielson <cfmd at bredband dot net>