# OpAmps For Everyone

## Ron Mancini

Language: English

Pages: 440

ISBN: 2:00050457

Format: PDF / Kindle (mobi) / ePub

OpAmps For Everyone by Ron Mancini

Guide for people looking to make use of opamps in any of their various uses. Especially useful for those DIY'ers looking to build simple amplifiers.

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10 Thevenin’s Theorem V OUT + V TH ǒ Ǔ R4 R2 +V R TH ) R 3 ) R 4 R1 ) R2 R4 R 1R 2 ) R3 ) R4 R 1)R 2 (2–15) The circuit analysis is done the hard way in Figure 2–10, so you can see the advantage of using Thevenin’s Theorem. Two loop currents, I1 and I2, are assigned to the circuit. Then the loop Equations 2–16 and 2–17 are written. R1 R3 R2 R4 I1 V VOUT I2 Figure 2–10. Analysis Done the Hard Way V + I 1ǒR 1 ) R 2Ǔ * I 2R 2 (2–16) I 2ǒR 2 ) R 3 ) R 4Ǔ + I 1R 2 (2–17) Equation

having a relationship to the real world, and some of them more attuned to the field of psycho-acoustics. White noise is in the middle of a spectrum that runs from purple to blue to white to pink and red/brown. These colors correspond to powers of the frequency to which their spectrum is proportional, as shown in Table 10–1. Table 10–1. Noise Colors COLOR Purple f Blue f White 1 Pink 1 f 1 f2 Red/Brown 132 FREQUENCY CONTENT 2 Noise Colors There are an infinite number of variations

(1/f) noise. From Paragraph 10.3.2 and 10.2.5, the noise from the resistors and the amplifier itself is: E Totalrms + Ǹ5.73 mV 2 ) 5.73 mV 2 ) 113.1 mV 2 + 113.1 mV rms (10–23) Signal-to-noise (dB) = 20 log(1V B 113.1 mV) + 20 log(8842) + 78.9 dB (10–24) So far, so good. The amplifier noise is swamping the resistor noise, which will only add a very slight pinkish component at low frequencies. Remember, however, that this noise Op Amp Noise Theory and Applications 143 Putting It All

ADC is given in Equation 12–1 where n is the number of significant bits contained in the ADC. RESOLUTION + 2 n (12–1) Some confusion exists about the word bits because the same word is used for binary bits and significant bits. Binary bits are ones and zeros used to calculate binary numbers; for example, a converter with 8 different digital states has 8 significant bits and 2n = 256 binary bits (see Figure 12–2). The voltage value of a single bit, called a least significant bit (LSB), is

factor in this design. The op amp input current is 100 pA, so it won’t cause much offset with a 383-kΩ feedback resistor (38.3 µV). The noise current and voltage are calculated later when the error budget is made. The gain, m, and the intercept, b, are not accurate because the exact resistor values were not available in the 1%-resistor selection chart. This is a normal situation, and in less demanding designs the small error either does not matter or is corrected someplace else in the signal