TSH112 STMicroelectronics, TSH112 Datasheet - Page 13

• Manufacturer Part Number: TSH112
• Description: WIDE BAND, LOW NOISE OPERATIONAL AMPLIFIERS
• Manufacturer: STMicroelectronics

Intermodulation Distortion
A non-ideal output of the amplifier can be de-
scribed by the following development :
V
due to a non-linearity in the input-output amplitude
transfert. In the case of V
component, C
the amplitude of the harmonics.
A one-frequency or one-tone input signal contrib-
utes to a harmonic distortion. A two-tones input
signal contributes to a harmonic distortion and in-
termodulation product.
This intermodulation product or intermodulation
distortion of a two-tones input signal is the first
step of the amplifier study for driving capability in
the case of a multitone signal.
In this case V
V
C
+
C
+
...C
V
C
+
C
+
2C
+
(3C
(A
+
(C
+
(3C
+
(3C
+
...C
In this expression, we can recognize the second
order intermodulation IM2 by the frequencies
(
ulation IM3 by the frequencies (2
(
out
out
out
O
2
O
2
(Asin
(A
3
3
1
+C
+C
2
sin
A
-
=
=
n
AB(cos(
3
3
3
n
1
=C
(V
/4)
A
B
(V
+2
2
3
+B
sin3
1
1
2
2
2
(Asin
(Asin
in
in
) and (
B/2)(sin(2
A/2)(sin(
0
1
)
)
+C
2
t+B
n
n
2
)/2-(C
1
) and (
t+Bsin
1
1
(V
3
t+B
sin
1
1
1
in
t+Bsin
t+Bsin
in
-
1
2
1
=Asin
)+C
3
(V
/2)(A
sin
2
2
)t-cos(
t+2A
in
2
1
1
1
t)
2
-
+2
2
) is the fundamental, C
) and the third order intermod-
(V
2
2
+C
2
cos2
2
2
2
)t-
in
1
2
t)
t)
t)
2
2
Bsin
)
t+Bsin
3
)t-
).
1/2
2
(Asin
+C
1
1/2
in
sin(2
=Asin t, C
1
3
t+B
2
sin(
(V
2
)t)
t+2B
in
1
2
2
t+Bsin
)
t, and :
cos2
3
1
1
+...+C
1
2
-
Asin
2
2
)t)
), (2
O
2
2
)t)
t)
2
n
is the DC
t)
(V
1
3
t)
in
1
n
)
A
n
n
2
is
),
TSH110-TSH111-TSH112-TSH113-TSH114
The following graphs show the IM3 of the amplifier
in two cases as a function of the output amplitude.
The two-tones input signal is achieved by the mul-
tisource generator Marconi 2026. Each tone has
the same amplitude. The measurement is
achieved by the spectrum analyser HP 3585A.
Both instruments are phase locked to enhance
measurement precision.
(fig.30): 3
280kHz)
A
(fig.31): 3
1.1MHz)
A
V
V
=+4, R
=+2, R
-100
-100
-60
-65
-70
-75
-80
-85
-90
-95
-60
-65
-70
-75
-80
-85
-90
-95
0.0
0
fb
740kHz
380kHz
fb
640kHz
3.2MHz
3.1MHz
1.2MHz
900kHz
80kHz
=680 , no C
=680 , C
rd
rd
Order Intermodulation
1
Order Intermodulation
0.5
Output Amplitude (V
fb
Output Amplitude (V
=2pF, R
fb
, R
2
L
=100 , Vcc=±6V
1.0
L
=100 , Vcc=±2.5V
3
peak
peak
)
)
1.5
4
(180kHz &
(1MHz &
13/19
2.0
5