Short Circuit Protection System At The Amplifier Output
- Single transistor provides short-circuit protection. Keith Szolusha, Linear Technology Corp, Milpitas, CA -October 16, 2003. 12V-output SEPIC has short-circuit protection. Figure 2 The short-circuit input and output current for the circuit of Figure 1 differ at different voltages.
- In the application I have in mind, the op amp output will be protected with a resistor in series and a diode/zener network in order to limit both the voltage and the current through the op amp. So of course my circuit could still be dangerous to the op amp but not as dangerous if no protection is used.
VOL 50Op Amp Input Overvoltage Protection: Clamping vs. IntegratedIntroductionHigh precision op amps enable system designers to create circuits that condition signals (amplify, filter, and buffer) while maintaining the precision of the original signal. When information is contained in very small variations of the signal, it is critical that op amps in the signal path perform their operation while contributing very little dc and ac error. The precision of the total system depends on maintaining the precision of the signal path.In some applications, a situation may occur in which the inputs of the op amp get driven by voltages outside the level of the supply voltages—this is called an overvoltage condition. For example, if an op amp is configured to run with its positive supply at +15 V and its negative supply at −15 V, any time an input pin goes more than one diode drop beyond those supply rails (such as ±15.7 V), the op amp's internal ESD protection diodes can be forward-biased and start conducting current. Excessive input current over long periods of time or even short periods of time, if the current is high enough, can damage the op amp. This damage can result in a shift in the electrical specification parameters beyond the data sheet's guaranteed limits; it can even cause a permanent failure of the op amp.
When system designers are faced with this possible situation, they often add overvoltage protection (OVP) circuits at the inputs to the amplifier. The challenge then is to add OVP circuitry without adding errors (loss of system precision).
In other words if your power supply is large enough to supply 200 amp, your current on a short circuit will be 200 amp.
Short Circuit Protection System At The Amplifier Output Definition
How Overvoltage Conditions Occur. Overvoltage Protection MethodOvervoltage conditions can be caused by a number of different situations.
Consider a system where a remote sensor is located in the field—for example, measuring fluid flow in a refinery and sending its signal through a cable to data acquisition electronics that reside at a different physical location. The first stage in the data acquisition electronics signal path can often be an op amp configured as a buffer or a gain amplifier.
Daniel BurtonDaniel Burton is an applications engineer at Analog Devices. He acquired his B.S.E.E. From San Jose State University and he has worked on sensing and precision linear signal paths for much of his career. Dan has been with Analog Devices since 2010, focusing on precision amplifiers and voltage references.Related Articles.FEB 2012Related Products.OVP and EMI Protected, Precision, Low Noise and Bias Current Single Op Amp.4 MHz, 7 nV/√Hz, Low Offset and Drift, High Precision Single AmplifierRelated Markets & Technology. The cookies we use can be categorized as follows: Strictly Necessary Cookies: These are cookies that are required for the operation of analog.com or specific functionality offered. They either serve the sole purpose of carrying out network transmissions or are strictly necessary to provide an online service explicitly requested by you.
Analytics/Performance Cookies: These cookies allow us to carry out web analytics or other forms of audience measuring such as recognizing and counting the number of visitors and seeing how visitors move around our website. This helps us to improve the way the website works, for example, by ensuring that users are easily finding what they are looking for. Functionality Cookies: These cookies are used to recognize you when you return to our website.
This enables us to personalize our content for you, greet you by name and remember your preferences (for example, your choice of language or region). Loss of the information in these cookies may make our services less functional, but would not prevent the website from working.
Targeting/Profiling Cookies: These cookies record your visit to our website and/or your use of the services, the pages you have visited and the links you have followed. We will use this information to make the website and the advertising displayed on it more relevant to your interests. We may also share this information with third parties for this purpose.
Hi all,I want to understand how to design an opamp circuit given what i want.e.g I want to implement short circuit protection, I already have a current sensing implemented using a current transformer, I know that X amount of current is expected (anything above the uC turns the system off but it is too slow, to account for inductive loads etc), I decide that 2X current is my limit for short circuit i.e any current above 2X is to be considered a short circuit. Hysteresis is to be +/- 0.25 times short circuit current (once short circuit has been detected the op-amp is not to deactivate until current falls down to 1.5X.)So given all this how do I approach op-amp design?
I am familiar with the 2 golden rules (Art of Electronics - Paul Horowitz) and I can solve circuits to some extent. However when it comes to right down intuitive designing I am at a loss. Normally I look at circuits, solve them and then tweak to produce desired results. I dont suppose this is how things are meant to be i.e learn circuits and equations and then solve where necessary. I was wondering how does one intuitively develop circuits around op-amps.
Any handy literature or how one starts solving the above problem would be a blast.thanks. One of the reasons the 741 was so beloved by universities (in spite of local critics) is the output is fairly tough, you could usually short it with no problems.Many newer op amps also have this feature, datasheets are your friend.The big thing to remember about op amps in general is they are self correcting. If the output can reach the goals the op amp can compensate for almost anything. The really big hitters with op amps in general are input response (how close the inputs can get to ± edges), the output ± response, slew rate, and frequency response. Click to expand.If you want fast action on short circuit current detection, then you should not be using an opamp.You would use a comparator instead, parts like LM393 or LM311 etc.If you want to learn how to design with them, the easiest way is to check out your design using simulator. Some colleges provide their students with access to SPICE simulator but one can always get a free one like LTSpice to use at home.Input your desire current profile as the sensed current to the comparator and watch how the comparator responses.
You can also tune the hysteresis characteristic too using the simulator.