anyone knows what are the purpose of amplifiers for bioelectronic instruments?

Question

Particularly differential, operational , electrometer and carrier amplifiers. plss. i badly need these info. thanks so much for help. =)

Answer 1

The purpose of amplifiers in general, is to boost the level of the low-voltages and currents produced by the body. Heart-beat voltages and currents are in the milli-volt and micro-amp regimes. Brain waves are also very tiny. In order for instruments to record and display such signals they need to be amplified.

Now, it is important in medical applications that the body be protected from accidental electric shock by these instruments. This is why these types of amplifiers are used (the ones mentioned in your list).

It is important to keep the bias currents from these amplifiers very very low (nano-amps, even pico-amps), so they will not shock the body. The types of amplifiers mentioned provide these low bias and offset currents. Bias and offset currents are currents that come out of the input side of the amplifier, right into the leads that are attached to the body for measuring heartbeats, brainwaves, etc.

Op amps configured as a differential or instrumentation amplifier provide very high gain, yet at the same time very low bias and offset current.

Electrometers are amplifiers with FET or MOSFET inputs that have the lowest bias currents available. Sometimes they have bias currents so low, you can actually measure them in terms of 1000s of electrons per second (versus 1 amp which is over a billion-billion electrons per second).

Carrier amplifiers only look at AC signals. There is no DC current that flows from the input signal source (somewhere on the body) to the amplifier, so absolutely no bias current flows). The signal modulates an RF carrier that is passed through capacitors to block any DC bias current. Once amplified and detected (rectified), the original signal is reproduced.

.