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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
Hi Shai, 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 (...)
Hi gays: 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 (...)
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?
The block may be used for thermal and star-up circuit for bandgap. It protects the power transistor(pass transistor). The circuit may be a LDO. There are bandgap, protection circuit and star-up ciruit blocks.
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 (...)
Hi... Ok, lets clarify ur Qs. If u mean a current source then u can use a current mirror using 2 transistors. If ur asking for a kind of protection circuit, there are many automatic so-called fuses available.
Hello, 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
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 55986 plz tell me how can i short ci
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
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. Now I
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
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.
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 The function
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
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
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 .. Regards, IanP
What type of protection you need? Output voltage, current, transistor, reverse voltage ... put your circuit for evaluation.
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 (...)
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 .. Regards, IanP
Hi Guys: 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/
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) .. Regards, IanP
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
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. ?
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
HFE is beta of the transistor IC = beta IB in active region cob i'm not sure
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.
wisepie, 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 (...)
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 (...)
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....
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.
FvM is correct when dealing with dedicated UARTs. However, if you are using a microcontroller and are willing to do a bit-banged serial communication in software without using the dedicated UART in the micrcontroller, then no transistors are required. This is possible because you can write the software to do the signal inversion for you. The
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.
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
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
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
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
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 (...)
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
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
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.
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, (...)
Hi, An active crowbar maybe. Or you could disconnect the load from the circuit by means of relay or transistor. Hope this helps. Tahmid.
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
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
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. Brian.
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.
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 .. IanP :wink:
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 (
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