129 Threads found on edaboard.com: Transistor Protection Circuit
What sought of protection u want to go for, current limit, over voltage for PDD,
For current limit u can simply build ur circuit around two PNP transistor.
For overvoltage detection also u can go for simple opamp with a zener voltage reference .
But decide wat protection u want to go for
Analog Circuit Design :: 26.03.2007 08:58 :: saurav_sdpl :: Replies: 3 :: Views: 1373
If in an regulator if the load ouput point has accidently been shorted to ground then a large amout of current will flow through the circuit and this can damage the pass transistor. Hence a short circuit protection can be used to detect this. Over current in a regulator can arise if the output load falls to a (...)
Analog Circuit Design :: 14.08.2007 08:36 :: Chethan :: Replies: 2 :: Views: 2257
I have a question about LDO over current protection. the question is following:
When the current of output transistor is to high, the protection transistor (PMOS) will pull up the gate of the power transistor to high voltage and close the power transistor. but the current flows (...)
Analog Circuit Design :: 03.02.2008 02:51 :: yxk :: Replies: 1 :: Views: 2277
What?s the idea behind the actual circuit? Load disconnect if input voltage lower than some fixed level? In this case I think you need to wire zener diode in series with the input of transistor?
Analog Circuit Design :: 24.07.2011 17:18 :: mister_rf :: Replies: 2 :: Views: 814
circuit in Red block will maintain 1.235 V at the output by maintaining the common mode level of npn transitors in the reference generation block. If you notice the connection to the bases of the input are having a resistor drop.Hence they will maintain a level at the input and at the emitter of the output transistor.
Mostly, this will work
Analog IC Design and Layout :: 14.04.2005 05:37 :: Vamsi Mocherla :: Replies: 6 :: Views: 759
The need for extra protection really depends on the process. Some of the processes I work with have very fragle NMOS transistors (drain silicide shorts to body) others are more robust. If the output transistor is large enough and is designed with the same rules as the ESD device then it could be OK. You really need to discuss this with the (...)
Analog IC Design and Layout :: 15.03.2006 06:29 :: DoctorProf :: Replies: 8 :: Views: 1070
Check this circuit:
Here you have a PNP transistor, that has 0,7V between emiter and base.
D1 is a diode, that could be a LED diode, with 1,7V diode tension.
Then, the value of current in collector-emiter from circuit, will be:
Ice = (Vdiode - Vbe) / Rlimit
So, for 500mA => Rlimit = (1.7-0.7) / 0.5 A = 1/0.5 = (...)
Analog Circuit Design :: 13.02.2007 19:01 :: penrico :: Replies: 2 :: Views: 549
I'm using a regulator with the schematic posted in the image attached, powered from a 30V source with 20000uF filter caps that can probably deliver more than 20A for short periods.
Unfortunately, the pass transistor blows instantly on short circuit. Q2 should limit the output current to 6-7A, but it seems it acts too slow, or the MOSF
Hobby Circuits and Small Projects Problems :: 18.12.2010 15:42 :: Eugen_E :: Replies: 9 :: Views: 1590
Battery is cut off by deep discharge protection circuit. Now to reset the system I need to short circuit the battery and charger positive terminals, on receiving a initial pulse from charger. On this pulse I need to make a path between charger and battery.
have a look at my circuit
plz tell me how can i short ci
Analog Circuit Design :: 04.05.2011 10:11 :: danidiesel :: Replies: 3 :: Views: 597
It?s a fairly simple scheme the current limiter. Think of the current-limiting circuit as a resistor that can change its resistance. It will automatically detect the amount of current that should be flowing through and change its resistance accordingly. The incoming current first goes through a current sensor (R1) whose output signal goes to a PNP
Electronic Elementary Questions :: 29.09.2011 04:44 :: mister_rf :: Replies: 5 :: Views: 442
It looks like a fairly ordinary triggered clamp but the problem lies in
the gain and speed, the clamp FET must actuate quickly enough to
protect the chip -and- have enough "hang time" to ride out the
HBM ESD source model's natural time constant, rather a whole
bunch of them since you're waiting for a few kV to be bled down
to a few volts.
Analog IC Design and Layout :: 02.12.2011 19:52 :: dick_freebird :: Replies: 4 :: Views: 817
I'd start with making the control logic based. You have
three states (closing, opening, where-it-sits). I would
make two SRFFs controlling two DPDT relays.
"Opening" switch event should set the "opening" 'flop
and reset the "Closing" flop. And vice versa.
Overcurrent should reset both (you don't care).
On power-up, "Closing" probably wants en
Electronic Elementary Questions :: 28.01.2013 18:00 :: dick_freebird :: Replies: 8 :: Views: 511
Fuse.pdf needs a correction. The most right transistor must be PNP type (BC212) and base and emiter must be interchanged othervice circuit doesn't work.
Electronic Elementary Questions :: 26.07.2004 00:54 :: Borber :: Replies: 19 :: Views: 3538
Again, as in Current Booster1, the vale of the resistor is wrong .. it should be somewhere between 3-10Ω ..
In this case current is limited by additional transistor, the 2N6049.
It happens when the voltage accross Rsc riches ≈0.65V and this tranistor starts to control Vbe of the power PNP transistor .. Iout≈0.65/Rsc
Analog Circuit Design :: 27.10.2005 21:35 :: IanP :: Replies: 4 :: Views: 888
Does anyone have any idea about bulk driven transistor. Just hear today and only know it's for low voltage design. Anyone has example or reference for this? Thanks
Analog Circuit Design :: 29.10.2005 00:43 :: bageduke :: Replies: 4 :: Views: 1244
If the current to the motor is below 200mA you can employ 555 timer in its monostable configuration and adjust the time in such a way that the motor will be on for 5 turns .. see picture below .. more you can find here:
If required current is >200mA you will need to add external NPN or PNP transistor to boos
Electronic Elementary Questions :: 30.10.2005 20:24 :: IanP :: Replies: 5 :: Views: 921
Q4 draws current from the base of the PNP transistor - Q6 ..
In NPN transistors current is pumped to the base, in PNP current is drawn from the base ..
Electronic Elementary Questions :: 03.12.2005 23:33 :: IanP :: Replies: 3 :: Views: 987
What type of protection you need?
Output voltage, current, transistor, reverse voltage ...
put your circuit for evaluation.
Analog Circuit Design :: 28.12.2005 14:07 :: Davood Amerion :: Replies: 4 :: Views: 762
Look at the layout first.
Usually output transistors and ESD transistors integrated in one large transistor that fingered by 40-50u with and surrounded by guard ring to prevent latch-up.
So when designer need to increase output driving capability he should cut some fingers from ESD part and connect them to output part. The total (...)
Analog IC Design and Layout :: 03.02.2006 03:01 :: Fom :: Replies: 5 :: Views: 835
Have a look at the H-Bridge circuit below; adding an inverter gate (or one NPN transistor) between inputs 1 and 2 will reduce the number of control inputs to just one, and will allow to drive the motor forward and reverse ..
However, you will not be able to STOP it ..
Hobby Circuits and Small Projects Problems :: 04.02.2006 09:01 :: IanP :: Replies: 8 :: Views: 3804
When I design the RF circuit, I would include a reversed biased diode model at the I/O port for surge protection. This is illustrated in Figure.1 where a complete I/O model used is presented.
I had received a feedback for an ESD designer to increase the number of series connected diodes to decrease the effective capacitance at the I/
RF, Microwave, Antennas and Optics :: 13.06.2006 03:08 :: hrkhari :: Replies: 2 :: Views: 1133
Take a look at the attached circuit ..
It will convert AC sine-wave to 0-5V square-wave, just increase the input resistor (R17) to, say, 4.7kΩ and connect protection diode between the transistor's base and the emitter (Cathode to Base) ..
Analog Circuit Design :: 14.07.2006 02:28 :: IanP :: Replies: 6 :: Views: 1345
The caliper uses a very small battery. I would try to avoid using the battery power to run the rest of the circuitry if at all possible.
Check if caliper put out power on line (1.55 Volt = silver oxide battey ?) via (MOS) transistor or pullup or have simple open collector output.
If caliper feeds power out to datalin
Electronic Elementary Questions :: 12.08.2006 06:59 :: xxargs :: Replies: 12 :: Views: 1164
place a low value series resistans and check voltage across it if > req. switch off the series pass transistor/ mosfet. for checking use opamp or single tansistor.
are you toking about inside the chip or external to the chip. ?
Analog Circuit Design :: 14.12.2006 01:58 :: manish12 :: Replies: 1 :: Views: 794
I've adapted the front end for this frequency counter (see diagram) from a design byPhil Rice VK3BHR and it works well. Now I want to put in some front end protection for the AT-41533-TR1 emitter follower front end transistor, it's rated at a max of 1.5V Vbe and the 74AC161 is good for a max input frequency of 200 MHz. L1 is supposed to help at h
Analog Circuit Design :: 27.01.2007 19:09 :: Gandalf_Sr :: Replies: 1 :: Views: 1624
HFE is beta of the transistor
IC = beta IB in active region
cob i'm not sure
Analog Circuit Design :: 28.04.2007 12:35 :: Yahia Muhammad :: Replies: 3 :: Views: 1062
Just capacitor could be not enough. Look there how old transistor ripple filter is done :
(r1 r2 c1 Q1)
Never worked with car supply bus , but suspect that spectrum of ripple and spike is too broad so C1 must be shunted with some capacitor enough to damp high frequency parts of noise spectrum.
Hobby Circuits and Small Projects Problems :: 28.05.2007 13:32 :: artem :: Replies: 5 :: Views: 1819
I believe that he diode on the right should be an ordinary diode. In this application, the lower terminal of the relay coil would be connected to the +16V supply. When the transistor turns off, the inductance of the coil will try to maintain current flow thrugh the coil. with no protection circuit, the voltage on the (...)
Electronic Elementary Questions :: 11.06.2007 17:42 :: Kral :: Replies: 6 :: Views: 740
the main idea here is that the transistor size depends on the application and need... if you study about the design of PLL, op amp etc... you would know the number of transistors and transistor sizes.... also in any IC level circuits the capacitors and resistors that you are seeing in discrete form are not used.... MOSFETs (...)
Analog Circuit Design :: 04.07.2007 21:47 :: A.Anand Srinivasan :: Replies: 10 :: Views: 728
i think that circuit would be just fine because it switches off the connection based on input power.... maybe you can change the bias conditions and the transistor for faster switching....
what more upgrades do you expect in this circuit....
Analog Circuit Design :: 22.07.2007 12:29 :: A.Anand Srinivasan :: Replies: 14 :: Views: 1830
Worst case scenario, alternator regulator fails shorted, relatively old battery, voltage input doubles.
maximum input on the lm2575 is 40 volts.
The circuit is not "dangerous", but it's failure may be spectacular.
As you only anticipate 1 amp at 12 volts, a transistor-Zenar regulator would add one more element of protection.
Analog Circuit Design :: 17.02.2008 12:13 :: Johansen :: Replies: 2 :: Views: 682
Does any one have a link or suggestions on how to make a rs232 transeiver with only one transistor(PNP 222A)? I have found one link that shows how to make one with two transistors ( )
Hobby Circuits and Small Projects Problems :: 01.05.2008 23:43 :: robismyname :: Replies: 4 :: Views: 3700
There are diodes with 200 pico-seconds response time.
Directional coupler and detector approach is used since the RF power transistor was invented, until now.
RF, Microwave, Antennas and Optics :: 02.10.2008 15:52 :: vfone :: Replies: 13 :: Views: 2371
I want to design a microcontroller based linear power supply with voltage and current reading, current limiting, etc, output voltage 0-15V, current 0-2A.
I sample with the uC ADC the output voltage and the voltage on the current sensing resistor every 1ms and display the voltage and current. The regulator itself is analog with the uC controlling
Analog Circuit Design :: 23.12.2008 16:40 :: Eugen_E :: Replies: 0 :: Views: 518
in our process, we stacked two mos transistors which can tolerate 2V operation range to be a 4V tolerate clamp, which is similar to your problem, in this clamp, the discharge path is through two serial connected mos transistor. and with an extra RC timer to control discharge timing, very efficient. much better than using the high voltage device to
Analog IC Design and Layout :: 27.03.2009 02:32 :: mdcui :: Replies: 4 :: Views: 2278
wt do u mean by "overload ckt" you want to provide the current limit to your circuit .
What is the maxium current you allow . if it's low you may use transistor cut off circuit for it
Analog Circuit Design :: 26.05.2009 23:37 :: dipnirvana :: Replies: 4 :: Views: 2565
the diodes are used for the protection of the transistors
so the voltage will always be in the intended direction and if the voltage polarity reversed it will protect the circuit
Professional Hardware and Electronics Design :: 29.05.2009 00:39 :: sau_sol :: Replies: 3 :: Views: 1210
I made a similar tach for small gas engines, I used an LM395 transistor as the input conditioner for an LM555. The LM395 is an industrial type transistor with gate protection up to 40V. Put about 5-10K in series with the gate and some zener protection to clamp over say 30V. Use bypass caps across the emitter/collector (...)
Analog Circuit Design :: 22.06.2009 14:01 :: Freddybaby :: Replies: 4 :: Views: 3478
what about a transistor buck regulator?, but you will need to get special high voltage
transistors, and you still need an inductor (though not a transformer)
what i'm thinking of is based on this
its something I thought of before and may do one day....
of course there is no safety isolation , b
Electronic Elementary Questions :: 06.03.2010 03:14 :: xaccto :: Replies: 23 :: Views: 9973
A charge pump can be used for disabling ESD protection during normal operation. For instance you could use an ESD protection transistor that is turned on unless its gate is biased highly positive (beyond Vdd) or negative.
Thanks for the discussion. ESD is always trouble for me too
When would this be used? Th
Electronic Elementary Questions :: 04.11.2009 04:39 :: snafflekid :: Replies: 2 :: Views: 706
the usual method is to use a directional coupler on the output circuitry of the final stage of the transmitter/amp. the detected RF is converted to DC by an appropriate diode detector and that changing DC voltage with increasing reflected power levels can be used to control a transistor that will supply the transmitter with its main DC voltage.
RF, Microwave, Antennas and Optics :: 24.05.2010 22:46 :: davenn :: Replies: 2 :: Views: 922
For me this circuit looks a little bit dodgy, as the forward voltage drop across the top BY398 diode may be to low to allow the transistor to be turned on ..
To provide protection and not to interfere with the transistor, I’d use two diodes each way, and perhaps increase the value of the base resistor from 47ohm to, (...)
Analog Circuit Design :: 29.06.2010 09:57 :: IanP :: Replies: 5 :: Views: 1549
An active crowbar maybe.
Or you could disconnect the load from the circuit by means of relay or transistor.
Hope this helps.
Analog Circuit Design :: 06.07.2010 05:18 :: Tahmid :: Replies: 5 :: Views: 1125
Hi everyone I am trying to boost the current output of LM7805. A circuit is available here :
On page 21 the circuit for Current boost with Short circuit protection is given.
My question is, in the given circuit, the transistor used is of low gain type. I would like to use TIP127 instead
Power Electronics :: 13.07.2010 11:12 :: eXnol :: Replies: 1 :: Views: 3025
Hi, deal all
I am designing a volgtage reference and it need a 0.1% initial accuracy,so i must trim out the variation.
I run the MC analysis and get a segma value,accordingly I set the trimming resistors range.But I realize the MC analysis can't cover all the process variations at least the package stress,as i know.Then most likely th
Analog IC Design and Layout :: 16.08.2010 23:36 :: wuxy :: Replies: 1 :: Views: 676
Starting from where? 110V AC, 230V AC, 0.001V DC and how much current does it have to supply, micro-amps or mega-amps? At what point does the over-voltage circuit cut in?
You need to give far more information to get a sensible answer. What on Earth is a 2N1595, I'll go look for it but it isn't a transistor I've ever come across before.
Electronic Elementary Questions :: 09.11.2010 06:06 :: betwixt :: Replies: 3 :: Views: 3686
Negative voltages as such won't affect the transistor, but with an inductive load, the negative voltage can be quite high and possibly exceed the transistor's voltage rating. It's a simple free-wheeling diode.
Electronic Elementary Questions :: 03.02.2011 03:38 :: FvM :: Replies: 13 :: Views: 7689
I wouldn’t try to find exact Ib current that produces Ic=70mA @ Vce<0.3V as if you use different transistor the values will be different ..
Try to use decent Ib current that will for sure produce saturation and then limit the Ic current to whatever level you need (70mA or so) with a resistor connected between and ..
Analog Circuit Design :: 17.11.2010 01:49 :: IanP :: Replies: 14 :: Views: 964
make a pic type low voltage 10bit mcu sence tickle charge etc in loop
in texas instruments they have also 0.9volt operating mcuz
play safe and that will lit red light on led for low battery ,u can make four five bar battery power showing light ledz
and also power some transistor for switches off your equipment
i have make this with two nokia bl5c (
Linux Software :: 29.12.2010 12:57 :: RAJAT AGGARWAAL :: Replies: 1 :: Views: 999
Most people use a simple free-wheeling diode. The voltage rating has to be higher than supply voltage, but isn't critical. You can use 1N4148 or similar SMD devices. If a very fast relay release is intended, you can connect all free wheeling diodes to the highest available supply voltage, if the respective relay drivers have a suffcient voltage rat
Analog Circuit Design :: 26.02.2011 15:46 :: FvM :: Replies: 5 :: Views: 1474