−3dB Commonly used for limits of bandwidth in amplifiers, indicating the points where:Ī. ☑dB The least noticeable change in audio levels, also used for the limits of bandwidth on high quality audio amplifiers. Commonly Encountered dB ValuesĠdB The reference level to which all +dB and −dB figures refer. Likewise losses due to circuits such as filters, attenuators etc. This can produce some very large numbers, but the total of individual gains expressed in dBs would be the sum of the individual gains:
#Op amp offset and attenuator series#
We may also share this information with third parties for this purpose.An advantage of using dBs to indicate the gain of amplifiers is that in multi stage amplifiers, the total gain of a series of amplifiers expressed in simple ratios, would be the product of the individual gains: We will use this information to make the website and the advertising displayed on it more relevant to your interests. 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. Loss of the information in these cookies may make our services less functional, but would not prevent the website from working. 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). Functionality Cookies: These cookies are used to recognize you when you return to 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. 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. They either serve the sole purpose of carrying out network transmissions or are strictly necessary to provide an online service explicitly requested by you. The cookies we use can be categorized as follows: Strictly Necessary Cookies: These are cookies that are required for the operation of or specific functionality offered.
There are other ways of increasing noise gain while keeping signal gain low, but that will have to wait for another RAQ. If there is at least 45° of phase margin at the selected noise gain, the amplifier will work fine, if less than 45° you might have trouble. Once the noise gain is determined it can be transposed to the open loop gain and phase plot to check for phase margin and stability. For example if an inverting amplifier has a signal gain of -0.5, it still has a noise gain of 1.5. The noise gain, which is the same for both inverting and noninverting amplifier configurations, is equal to the noninverting gain equation. Remember that it is the noise gain, not the signal gain that determines amplifier stability. Large feedback resistors, along with the amplifier's input and stray capacitance, can introduce a pole in the amplifiers feedback response, this causes additional phase shift, which reduces the amplifiers phase margin and can lead to instability.Ī more important consideration is noise gain and how it relates to amplifier stability. This has several implications: more system noise, larger offset voltages and stability. The first is when very large values of feedback resistance are used. I mentioned that some precautions must be considered when using amplifiers as attenuators.
So you can actually use both inverting and noninverting op amp configurations as attenuators. You could also use a differential amplifier or a difference amplifier both use the gain equation G = RF/RG. Well not necessarily as mentioned previously a passive attenuator in front of a noninverting amplifier would work and provide a noninverted output. A quick inspection indicates that the only viable configuration for an amplifier/attenuator must be inverting. This is because the inverting gain equation is G = –RF/RG, while the noninverting gain equation is G=(RF/RG)+1. Therefore the assumption is the amplifier must be configured as an inverter. When using an amplifier as an attenuator, the amplifier has less than unity gain (G < 1). A few precautions must be taken, however.
#Op amp offset and attenuator full#
Using a passive attenuator in front of an op amp, or using the amplifier itself as an attenuator takes full advantage of this feature. One very useful feature of an op amp is impedance transformation. It seems counter intuitive on the surface, but there are actually some very good reasons why one might want to do this. Can I use an amplifier as an attenuator? Answer: