RHF310AK01V 데이터 시트보기 (PDF) - STMicroelectronics
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RHF310AK01V Datasheet PDF : 25 Pages
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RHF310A
Bias of an inverting amplifier
Where the input is Vin = Asinɷt, C0 is the DC component, C1(Vin) is the fundamental and Cn is the amplitude of
the harmonics of the output signal Vout.
A one-frequency (one-tone) input signal contributes to harmonic distortion. A two-tone input signal contributes to
harmonic distortion and to the intermodulation product.
The study of the intermodulation and distortion for a two-tone input signal is the first step in characterizing the
driving capability of multi-tone input signals.
In this case:
Vin = A sinω1t+ A sinω2t
Therefore:
Vout = C0 + C1 (A sinω1t + A sinω2t) + C2 (A sinω1t + A sinω2t)2…+ Cn (A sinω1t + A sinω2t)n
From this expression, we can extract the distortion terms and the intermodulation terms from a single sine wave.
• Second-order intermodulation terms IM2 by the frequencies (ω1-ω2) and (ω1+ω2) with an amplitude of
C2A2.
• Third-order intermodulation terms IM3 by the frequencies (2ω1-ω2), (2ω1+ω2), (-ω1+2ω2) and (ω1+2ω2) with
an amplitude of (3/4)C3A3.
The intermodulation product of the driver is measured by using the driver as a mixer in a summing amplifier
configuration (Figure 27. Inverting summing amplifier). In this way, the non-linearity problem of an external mixing
device is avoided.
Figure 26. Inverting summing amplifier
Vin1
R1
Rfb
Vin2
R2
_
Vout
+
1 kΩ
R
6.4
Bias of an inverting amplifier
A resistance is necessary to achieve good input biasing, such as resistance R shown in Figure 28. Compensation
of the input bias current.
The value of this resistance is calculated from the negative and positive input bias current. The aim is to
compensate for the offset bias current, which can affect the input offset voltage and the output DC component.
Assuming Iib-, Iib+, Rin, Rfb and a 0 V output, the resistance R is:
R = -RR---ii-nn---×+----R-R---ff-b-b--
DS6201 - Rev 7
page 14/25
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