TS615IPWT(2004) View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TS615IPWT Datasheet PDF : 36 Pages
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Intermodulation Distortion Product
TS615
5 Intermodulation Distortion Product
The non-ideal output of the amplifier can be described by the following series, due to a non-linearity in the
input-output amplitude transfer:
Vout
=
Co
+
C1Vin
+
C2
Vin2…
+
Cn
V
n
in
where the single-tone input is Vin=Asinωt, and C0 is the DC component, C1(Vin) is the fundamental, Cn is
the amplitude of the harmonics of the output signal Vout.
A one-frequency (one-tone) input signal contributes to a harmonic distortion. A two-tone input signal
contributes to a harmonic distortion and an intermodulation product.
This intermodulation product, or rather, the study of the intermodulation distortion of a two-tone input
signal is the first step in characterizing the amplifiers capability for driving multi-tone signals.
The two-tone input is equal to:
Vin = A sinω1t + B sinω2t
giving:
Vout = C0 + C1(A sin ω1t + B sin ω2t) + C2(A sin ω1 t + B sin ω2t)2… + Cn(A sin ω1t + B sin ω2t)n
In this expression, we can extract distortion terms and intermodulations terms from a single sine wave:
second-order intermodulation terms IM2 by the frequencies (ω1-ω2) and (ω1+ω2) with an amplitude of
C2A2 and third-order intermodulation terms IM3 by the frequencies (2ω1-ω2), (2ω1+ω2), (−ω1+2ω2) and
(ω1+2ω2) with an amplitude of (3/4)C3A3.
We can measure the intermodulation product of the driver by using the driver as a mixer via a summing
amplifier configuration. In doing this, the non-linearity problem of an external mixing device is avoided.
Figure 46. Non-inverting summing amplifier
1kΩ
Vin1
1:√2
50Ω
400Ω
49.9Ω
1kΩ
49.9Ω
North Hills
0315PB
Vin2
1:√2
50Ω
400Ω
North Hills
0315PB
49.9Ω
1kΩ
1kΩ
11
+
+Vcc
1/2TS615
10 _
13
Rfb1
Rg1
Vout diff.
Rg2
Rfb2
_
1/2TS615
+
-Vcc
49.9Ω
49.9Ω
33Ω
33Ω
√2:1
100Ω
50Ω
North Hills
0315PB
49.9Ω
17/36
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