Rectifier diode

Status
Not open for further replies.

Thread Starter

DexterMccoy

Joined Feb 19, 2014
429
But when u have these clamping diodes only on the negative cycle voltage, it clips or shunts the negative cycle off which means the signal is a pulsing half wave form going to the input of a transistor or op amp. Yes the diode protects it from a large negative voltage but it changes the waveform into a pulsing waveform
I'm talking about the single end diode on the output or input of opamps or transistors, to protect the op amp and transistor from a Large negative voltage or negative cycle from damaging it

When you put a diode to clamp the negative cycles voltage, you are changing the waveform into a pulsating positive cycle half waveform because the negative cycle has be clipped off

So you're getting only "Positive pulses at time intervals" into the input of a op amp

Why would you want "Positive pulses at time intervals" into the input of a op amp? because you have clipped off the negative cycle

They are called single ended negative clipping diodes circuit
 

daviddeakin

Joined Aug 6, 2009
207
But when u have these clamping diodes only on the negative cycle voltage, it clips or shunts the negative cycle off which means the signal is a pulsing half wave form going to the input of a transistor or oop amp. Yes the diode protects it from a large negative voltage bbut it changes the waveform into a pulsing waveform
But if CR19 was not there, the transistor would still switch on ONLY during the positive pulses, so it does not matter if the negative cycles are clipped before the transistor; the transistor would appear to clip them anyway.

The circuit is a peak-hold detector. It discharges C12 during positive signals to create a (dirty) DC voltage across C12 that is proportional to the peak AC signal.

It works in the same basic way as the circuit below: (except your circuit reduces the DC voltage with each pulse, rather than increasing it)
 

Thread Starter

DexterMccoy

Joined Feb 19, 2014
429
But an amplifier NPN transistor can swing both polarities , positive cycle and negative cycle

But if the negative cycle is more than -5 volts , the NPN transistor will get damaged? the negative cycle will damage the reverse breakdown

Same thing for the input of Op-amps, is there is transistor internally inside the op amps on the input pin, these transistors will get damaged if the Negative cycles voltage is to large?

will damage the reverse break voltage for the Op-amps input pin? which is what MAX negative voltage can you apply to a 741 op amp? or a LM101 amplifier IC chip?

I think LM101 amplifier IC chips didn't have protection circuits internally inside the Op amps like newer Op amp amplifier IC chips do, So you had to put a clipper Diode for the negative cycles voltage to protect the Op amps Input section internally from getting damaged

Because we use Op amps and Transistor to do amplifications , swinging both positive and negative cycles, much more they -5volts on the negative cycle I have see that didn't damage the transistor or op amps

Maybe cause they use Power transistors?
 

shortbus

Joined Sep 30, 2009
10,045
You keep asking impossible questions about a certain circuit. Since no one on this forum was the designer or the company that made the circuit, the questions can't really be answered.

Every designer/company has a way of working. There is NO SINGLE way of doing a circuit. Some times it is done differently to get around a patent. Some time because it is the way the company did it in the past. Some time it is because of the component hardware the circuit is controlling. It is time that you learn to accept this. If you get another companies board or a newer version of this type board to troubleshoot, are you going to go through this procedure all over again?
 

daviddeakin

Joined Aug 6, 2009
207
But if the negative cycle is more than -5 volts , the NPN transistor will get damaged?
More than 5V below the emitter. If the emitter is at -10V, then the base must not go below -15V. If the emitter is at +100V, then the base must not go below +95V. etc.

which is what MAX negative voltage can you apply to a 741 op amp? or a LM101 amplifier IC chip?
Probably a few volts below the negative rail.
 
Supply rail -22V, Found using some modern fangled thing called google, apparently the component has a datasheet. It is full of all kinds of numbers, one of which says +-22V supply rail.
Some people struggle to work out how to use google,I wish they would make it easier to find things!! maybe have a thought reader or something? anyway I spent the day working out how to make it go get the information and have placed the link below, this will save you the pain I had to endure to find it
http://pdf1.alldatasheet.com/datasheet-pdf/view/9027/NSC/LM741.html
I have asked dad to pay for a flight for me so I can come over and use google for you, but no luck so far sorry

LG
 

Thread Starter

DexterMccoy

Joined Feb 19, 2014
429
daviddeakin

When a signal/waveform has the negative cycle clipped or clamped , that goes into a transistors base or Op amps input, what does the output look like?

Is the output's waveform negative cycle clipped/clamped

Because the Positive peak is going to be different then the negative cycles peak because it's been clipped off or clamped

The output of the transistor or op amps is going to have different Peaks voltage for the positive cycle and negative cycle because of the INPUTS Negative cycles has be clipped and clamped off?

Does Designers Clips and Clamp off the negative cycle because it's going to a comparators input or an amplifiers input?
 
Status
Not open for further replies.
Top