BJT Amplifier Output Votlage Swing

Started by panfilero in sci.electronics.basics10 years ago 12 replies

I'm having a hard time understanding the "negative swing" of a common-emitter amplifier. There is a website called thesignalpath.com where a BJT...

I'm having a hard time understanding the "negative swing" of a common-emitter amplifier. There is a website called thesignalpath.com where a BJT amplifier is described. The set up is a BJT with a collector resistor, an emitter resistor, 2.5V and -2.5V supplies, and we're taking the output off the collector. The BJT has a Vce,sat = 0.2V According to the website maximum Vout = Vdd positive...


How can I measure the output impedance of an operational amplifier ?

Started by Martin Sigwald in sci.electronics.basics15 years ago 15 replies

I need to physically measure the output impedance of an operational amplifier (LM741), working as an inverter and with a capacitor as load. Any...

I need to physically measure the output impedance of an operational amplifier (LM741), working as an inverter and with a capacitor as load. Any ideas on how to do this? Impedance analyzer is out of the question. Thanx in advance.


lockin amplifier question

Started by jeremy in sci.electronics.basics15 years ago 5 replies

hi i am using a lockin amplifier for the 1st time other than a canned college lab demo i have a 5mV signal from a strain gage that is driven...

hi i am using a lockin amplifier for the 1st time other than a canned college lab demo i have a 5mV signal from a strain gage that is driven with 10Vpp at 1kHz or whatever i choose. the 5mV is increased to 5.01mV when i add some weight to the arm the gage is weighing. i wanted to increase sensitivity of this reading with the LIA since there is noise in the next digit, i.e. i read 5....


Building a class A audio amplifier - no audio out

Started by Anonymous in sci.electronics.basics13 years ago 68 replies

I tried to build this Class A amplifier circuit as a learning experience: http://www.techlib.com/electronics/audioamps.html#class-a with the...

I tried to build this Class A amplifier circuit as a learning experience: http://www.techlib.com/electronics/audioamps.html#class-a with the following modifications: 1. I have no MPSW45, so I built a Darlington out of a 2N2222 and TIP31A. 2. 150k resistors: I only had two 100k resistors in my collection. But as long as they're identical, should work...??? 3. speaker: I had only a 10W...


Power output of TBA820M (audio amplifier chip)?

Started by Adam Funk in sci.electronics.basics5 years ago 8 replies

Does anyone know a formula for calculating the power output of the TBA820M audio amplifier IC? The data sheet gives the...

Does anyone know a formula for calculating the power output of the TBA820M audio amplifier IC? The data sheet gives the following examples: supply (V) load (?) output (W) 12 8 2 9 4 1.6 9 8 1.2 6 4 0.75 3.5 4 0.25 but the output isn't consistently proportional to V^2/R (which was my


Why use amplifier with adc?

Started by Anonymous in sci.electronics.basics9 years ago 5 replies

I don't know very well how adc works, so i have a question. Most adc have a Vref pin that defines Vin range of adc. Vin range of adc is then...

I don't know very well how adc works, so i have a question. Most adc have a Vref pin that defines Vin range of adc. Vin range of adc is then divider for 2^n (n=resolution) to obtain LSB. If i resize Vref, new Vin range (smaller) is divided for 2^n, so LSB has smaller value.If i have a sensor, why i shoud use amplifier to drive Vin pin of adc?can i resize Vref as i like (or there is a limit)? ...


Tube Amp

Started by Dave.H in sci.electronics.basics14 years ago 13 replies

Hi, I'm looking for plans for a 1 or 2 tube low voltage amplifier to go with a regenerative radio. Does not have to be the best, but needs to...

Hi, I'm looking for plans for a 1 or 2 tube low voltage amplifier to go with a regenerative radio. Does not have to be the best, but needs to drive at least 250 mW speaker, preferably 1 watt or more. Thanks, Dave Australia


For amdx: - Kleijer amplifier reworked.

Started by Fred Abse in sci.electronics.basics9 years ago 18 replies

Examination of a full model of the whole circuit revealed that the parallel input resistance would actually go negative somewhere around 1MHz,...

Examination of a full model of the whole circuit revealed that the parallel input resistance would actually go negative somewhere around 1MHz, exactly where dependent on source resistance. I got interested, and finished up doing a rework, addressing: Negative input resistance. Gain not unity, as claimed. Actually 4dB. Output operating point nowhere near Vcc/2, hence reduced output sw...


Using mobile phone as an internet radio

Started by jim stone in sci.electronics.basics10 years ago 136 replies

Not being able to find a small internet radio to buy we liked, we got mobile phone with which we link with wi-fi to a modem router, and use it...

Not being able to find a small internet radio to buy we liked, we got mobile phone with which we link with wi-fi to a modem router, and use it as an internet radio. Keeping the phoned plugged into its charger all the time, we are using it to play *all-day* background classical music through an amplifier and speakers. Since the phone has no 'moving parts' unlike a computer, we are wonde...


audio amplifier output transistors

Started by Anonymous in sci.electronics.basics14 years ago 8 replies

I noticed that TR7 is PNP and TR9 is NPN here: http://www.dself.dsl.pipex.com/ampins/dipa/dpafig1.gif Then over here, TR7 is NPN and TR9 is...

I noticed that TR7 is PNP and TR9 is NPN here: http://www.dself.dsl.pipex.com/ampins/dipa/dpafig1.gif Then over here, TR7 is NPN and TR9 is PNP: http://www.dself.dsl.pipex.com/ampins/dipa/dpafig33.gif Are these correct, or in error? Also - for building audio amps "on the cheap", would TIP41C/TIP42C do for output transistors in these schematics? Thanks, Michael