# symbol identification - google has failed this noob

Discussion in 'Homework Help' started by daveyjones97, Apr 3, 2013.

1. ### daveyjones97 Thread Starter Active Member

Oct 21, 2011
46
1
hi, thanks for taking the time to look at this. i have minimal electrical knowledge, but would like to learn so downloaded the "EveryCircuit" app for android.
the problem i have is identifying 2 of the component symbols:

http://www.flickr.com/photos/46867082@N02/8613450860/

http://www.flickr.com/photos/46867082@N02/8612344863/

i have emailed the developer but have had no response and the web address doesnt work either. its a shame as component i.d and simple instructions would make the app even better and as someone who only ever has free time (whatever that is) at work sites like yours and apps like everycircuit are the only way for me to learn.

2. ### Papabravo Expert

Feb 24, 2006
11,737
2,483
The two symbols are:
1. Voltage Controlled Voltage Source
2. Voltage Controlled Current Source

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3. ### WBahn Moderator

Mar 31, 2012
23,160
6,973
These are "controlled sources" or "dependent sources".

The first is a voltage-controlled voltage source. Whatever voltage appears between the terminals on the left is multiplied by the gain (the "2V/V" in this case) and that is what is produces across the terminals on the right. So, if you have the terminals on the left are connected across a 1kΩ resistor in a circuit and that circuit has 3mA flowing in it (from the + to the -), then it has 3V across it. Your output on the right would then be 6V because you get 2V out per 1V in (hence, 2V/V).

The second is a voltage-controlled current source. The basic idea is the same except that the source on the right produces a current output instead of a voltage output. Using the example above, your input would still be 3V, but your output would be 6mA because you get 2mA out per 1V in (hence, 2mA/V).

Another name for the first is a "voltage amplifier" while another name for the second is a "transconductance amplifier". The other two alternatives are for an input current to control an output voltage or an output current. In the former case it would be called a "current amplifier" and in the latter case it would be called a "transconductance amplifier".

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