ETC P10964EJ2V0AN00

GENERAL-PURPOSE HIGH-FREQUENCY
WIDEBAND AMPLIFIERS
µPC1675G, µPC1676G, µPC1688G
1.
GENERAL
The µPC1675G, µPC1676G and µPC1688G are silicon monolithic ICs developed as general-purpose high-
frequency wideband amplifiers.
These ICs are based on the µPC1651G packaged in a 4-pin disc mold. The present ICs are each packaged in
a 4-pin mini-mold suitable for surface mounting on higher density print board. (the µPC1651G has been discontinued).
The features of these amplifier ICs are:
<1> The 4-pin mini-mold package as shown in Figure 1 substantially reduces the mounting area.
<2> The ICs are supplied on an embossed tape conforming to EIAJ’s “Taping Dimensions of Electronic Components
(RC-1009)”. This embossed tape is 8 mm wide, and suits automatic mounting.
<3> The following three models are available, classified by power gain.
µPC1675G: GP = 12 dB TYP., NF = 5.5 dB TYP. (@f = 500 MHz)
µPC1676G: GP = 22 dB TYP., NF = 4.5 dB TYP. (@f = 500 MHz)
µPC1688G: GP = 21 dB TYP., NF = 4.0 dB TYP. (@f = 500 MHz)
<4> All the models can operate at high frequency and in wide band.



µPC1675G: 1900 MHz TYP.
µPC1676G: 1200 MHz TYP.
µPC1688G: 1100 MHz TYP.
frequency point of –3 dB gain from flat gain
<5> Input/output matched to ZO = 50 Ω.
<6> Single power source (VCC = 5 V TYP.)
Figure 1. Package (unit: mm)
Figure 2. Internal Equivalent Circuit
+0.2
+0.1
0.4 –0.05
+0.1
0.4 –0.05
2.8 –0.3
+0.2
3
R6
Q2
(1.9)
0.95
Q3
Q7
4
Q4
+0.1
5˚
0.4 –0.05
+0.1
0.6 –0.05
5˚
R5
Q1
Q5
R3
Pin connections
1. GND
2. Output
3. VCC
4. Input
5˚
Document No. P10964EJ2V0AN00 (2nd edition)
Date Published February 1996 P
Printed in Japan
+0.1
0.16 –0.06
0 to 0.1
0.8
+0.2
IN
1.1 –0.1
OUT
Q6
1
(1.8)
+VCC
R1
0.85
2.9 +– 0.2
2
1.5 –0.1
5˚
R2
R7
C
R4
Q8
GND
©
1996
2.
CIRCUIT CONFIGURATION
Figure 2 shows the internal equivalent circuit of the µPC1675G/µPC1676G/µPC1688G.
The equivalent circuits of all the models are the same, and gain is set by changing R2, R3, R4, and R7. Like the
µPC1651G, each circuit is designed as multiple negative feedback amplification from the output block to the base
and emitter of Q1. MOS capacitance C is connected to the emitter of Q7 to peak the frequency characteristics.
The basic circuit is the single-end multiple negative feedback amplification type shown in Figure 3. This circuit
configuration has the following features:
Figure 3. Circuit Configuration
RF2
RL
RS
RE1
~
RE2
RF1
<1> Excellent frequency-gain characteristics.
<2> The input/output impedance and gain can be determined by the feedback resistance.
<3> Excellent noise characteristics because the resistance at the emitter of transistor in the input stage is lower than
that of the differential circuits.
<4> Excellent impedance matching with external circuits as compared with differential circuits, improving the output
efficiency and decreasing the noise.
As the first approximation, the input/output impedances Ri and Ro, and gain S21 of the circuit in Figure 3 can be
generally determined by the following equation.
Ri =
Ro =
(RF2 + RE2) RE1 · R
RE1 · R + RE2 (RF1 + RE1 + R)
(RF1 + RE1) RE2 · R
RE1 (RE2 + RF2 + R) + RE2 · R
S21 =
RF1 + RE1
RE1
············ (1)
············ (2)
············ (3) (where RS = RL = R)
By following modification on Figure 3, multiple negative feedback amplifier is realized as monolithic IC shown in
Figure 2.
2
<1> To increase the feedback loop gain, the final stage Q6 and Q7 are connected in a Darlington configuration. Q6
is connected to R5 to optimize the bias current.
<2> As for feedback to the emitter of Q1 from the collectors of Q6 and Q7, the impedance and voltage are adjusted
by the emitter-follower configuration of Q2 and the diodes of Q3 through Q5.
<3> Q8 diode rises up Q7 emitter potential to supply bias current to Q1 base through feedback path.
Simulation results of input/output impedance and gain vs. R3 , R4 feedback resistance are shown below (the result
of this simulation is slightly different from the calculation using equation 1 through 3 because the circuit configuration
is more complicated than Figure 3. R3 is equivalent to RF2 in Figure 3, and R4 is equivalent to RF1).
Figure 4. Input/Output Impedance vs.
Figure 5. Forward Transmission Gain vs.
Feedback Resistor
Negative Feedback Resistor
75
R3 = 140 120 100
80 (Ω)
50 Zout



25
0
Zin
S21 (dB)
Zin , Zout (Ω)
20
R3 =
140
120
15



100
80
(Ω)
100
150
200
R4 (Ω)
100
150
200
R4 (Ω)
As shown in Figures 4 and 5, the input/output impedance and gain can be easily controlled by feedback resistors
R3 and R4.
Respectively, the input/output impedance is set to 50 Ω for wideband operation, and R3 and R4 to 120 Ω and 200
Ω to obtain a sufficient gain.
3
3. CHARACTERISTICS
This chapter compares the measured characteristics of
µPC1675G and µPC1676G as representative IC. The
absolute maximum ratings and electrical characteristics are shown in Table 1 and 2. (Test circuit is shown in Figure
20.)
Table 1. Absolute Maximum Ratings (TA = +25 ˚C)
Parameter
Symbol
Rating
Unit
6
V
Supply voltage
VCC
Total dissipation
PT
200
mW
Operating temperature range
Topt
–40 to +85
˚C
Storage temperature range
Tstg
–55 to +150
˚C
Table 2. Electrical Characteristics (VCC = 5 V, TA = +25 ˚C)
Specifications
Parameter
Symbol
µPC1675G
Condition
µPC1676G
Unit
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
Supply current
ICC
Without signal
12
17
22
14
19
24
mA
Power gain
GP
f = 500 MHz
10
12
14
19
22
24
dB
Noise factor
NF
f = 500 MHz
Upper-limit operating frequency
fu
–3 dB from gain flat
Isolation
ISL
Input return loss
–
5.5
7.0
–
4.5
6.0
dB
1600
1900
–
1000
1200
–
MHz
f = 500 MHz
21
25
–
24
28
–
dB
RLin
f = 500 MHz
9
12
–
9
12
–
dB
Output return loss
RLout
f = 500 MHz
8
11
–
6
9
–
dB
Output power
PO
f = 500 MHz, Pin = 0 dBm
2
4
–
3
5
–
dBm
Figures 6 through 11 and Figures 12 through 17 show the characteristic curves including the voltage characteristics
and temperature characteristics of the µPC1675G and µPC1676G. Figure 18 shows the impedance characteristics
(Smith chart).
4
Figure 6. G P, NF vs. f Characteristics
Figure 7. Isolation vs. f Characteristics
of µPC1675G
of µPC1675G
0
5.5 V
VCC = 5 V
GP
12
4.5 V
8
5.5 V
NF
Isolation ISL (dB)
Noise factor NF (dB)
Power gain GP (dB)
5.0 V
5.0 V
4.5 V
4
–10
–20
–30
0
60
100
200
500
1000
2000
60
100
200
Frequency f (MHZ)
of µPC1675G
VCC = 5 V
RLin
RLout
–20
VCC = 5 V, f = 500 MHZ
5
0
Output level Po (dBm)
Input return loss RLin (dB)
Output return loss RLout (dB)
2000
Figure 9. Input/Output Characteristics
of µPC1675G
–30
60
1000
Frequency f (MHZ)
Figure 8. Return Loss vs. f Characteristics
–10
500
0
–5
–10
–15
100
200
500
Frequency f (MHZ)
1000
2000
–20
–30
–25
–20
–15
–10
5
10
Input level Pin (dBm)
5
Figure 10. IM 3 Characteristics
Figure 11.
of µPC1675G
G P vs. Temperature Characteristics
of µPC1675G
20
VCC = 5 V
f = 0.1 GHZ
f = 0.5 GHZ
f = 1.0 GHZ
f1 = 500 MHZ
f2 = 504 MHZ
–50
IM3 level (dB)
–40
Power gain GP (dB)
15
5.5 V
5.0 V
–30
4.5 V
10
5
–20
0
–10
–20
–10
Output level Po (dBm)
–25
0
+25
+50
Ambient temperature TA (˚C)
+75
0
Figure 12. GP, NF vs. f Characteristics
Figure 13. Isolation vs. f Characteristics
of µPC1676G
of µPC1676G
30
0
VCC = 5.5 V
VCC = 5 V
5
GP
20
4.5 V
VCC = 5.5 V
NF
10
4.5 V
0
0
60
5.0 V
–10
–20
–30
60
100
200
500
Frequency f (MHZ)
6
Isolation ISL (dB)
Noise factor NF (dB)
10
Power gain GP (dB)
5.0 V
1000
2000
100
200
500
Frequency f (MHZ)
1000
2000
Figure 14. Return Loss vs. f Characteristics
Figure 15. Input/Output Characteristics
of µPC1676G
of µPC1676G
VCC = 5 V, f = 500 MHZ
10
Output level PO (dBm)
Input return loss RLin (dB)
Output return loss RLout (dB)
VCC = 5 V
0
RLout
–10
–20
RLin
0
–10
–30
60
100
200
500
1000
2000
Frequency f (MHZ)
–20
–30
–20
–10
0
Input level Pin (dBm)
Figure 16. IM3 Characteristics of µPC1676G
Figure 17. GP Temperature Characteristics
of µPC1676G
–30
Power gain GP (dB)
IM3 level (dB)
–40
5.5 V
5.0 V
VCC = 5 V
f = 0.1 GHZ
f = 0.5 GHZ
f = 1.0 GHZ
40
f1 = 500 MHZ
f2 = 504 MHZ
–50
30
20
4.5 V
10
–20
–25
–10
–20
–10
Output level PO (dBm)
0
+25
+50
Ambient temperature TA ( C)
+75
0
7
1.4
1.2
–70
0.37
0.13
0.38
0.39
0.12
0.11
–100
–90
0.36
0.04
–80
4
0.3
6
0.1
0.35
0.15
1.0
1.6
0
1.8
0.2
32
18
0.
3
0.3 7
0.1
–6
0.40
0.10
–11
0
0.4
1
0.0
0.4
9
0 2
–1 .08
0.
20
4
0
00 3
.0
7
30
0.8
2.0
0
0.9
0.6
3.
0
1.
10
1.
0
50
0.2
(
0
1.
POS
14
ITIV
0
ER
EA
CT
A
––+JX NCE
ZO––
CO
M
PO
N
)
0.4
20
10
5.0
4.0
3.0
2.0
1.8
1.6
1.4
1.2
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
100 MHz
20
0.2
–1
0
–5
0.7
)
20
0.6
(
0.6
0.1
0.6
0.
0. 31
19
NE
G
0.4
0
–4
E
IV
AT
0.8
4.0
2.0
5
0.
44
0.
06
0.
0.6
1.8
1.6
0.2
1.0
0.9
0.8
1.4
0.7
0.37
0.13
0.8
1.6
0.7
1.4
1.2
1.0
0.9
0
0.4 5
5
0.6
1.8
2.0
5
0.
0.4
0
E
IV
AT
(
E
NC
TA
AC – JX
––
RE
––ZO
0.6
15
)
1.
0
100 MHz
50 MHz
0.
8
200 MHz
3.
0
1.
0
4.0
6.0
1.2 GHz
)
0.
8
0.2
8
0.2
2
–20
6.0
NE
G
0
3THS T NGLE OF
6
0.0
A
NG
0.4
4 ELE –160
0.0WAV
0
0
5
15
0
–
.
0
44
0. 06 40
ENT
ON
MP
0. –1
CO
0.8
.45
0
0.0
50
0.
0.1
0.3 7
3
0.2
00 9
0.2
0.3
1
–3
0.2 0
0
0
0.
5
0.6
0.27
0.23
E
NC
TA
AC – JX
––
RE
––ZO
REACTANCE COMPONENT
R
––––
0.2
ZO
50
0.
4
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
50
20
10
5.0
4.0
3.0
2.0
1.8
1.6
1.4
1.2
1.0
0.9
0.8
0.1
0.4
0.1
0.4
46
1.
0
10
20
50
0.4
0.25
0.25
0
EO
3 S
6
0E.0NGTH ANGL
0.4
4 VEL –160
0.0WA
0
0
5
5
–1
0.0
44
0. 06 40
ENT
ON
.
1
MP
0
–
CO
10
0.2
(
0.0
0.4 5
5
0
1.
)
POS
14
ITIV
0
ER
EA
CT
A
––+JX NCE
ZO––
CO
M
PO
N
6
15
0
WAVELE
NGTH
S TO
0.02 WARD
G
0.0 ENER
0.48
3
AT
0.4
NT IN
0.0 OR
DEG
7
4
REE
0.4
S
4
0.
8
0.6
0.2
0
0.01
0.49
0.48
0
0.49
0.01
.0W2ARD LOAD
0O
REFLECTION COEFFCIE
4.0
0.26
0.24
.45
8
0.
–11
0.38
0.39
0.12
0.11
–100
–90
0.36
0.04
–80
0.35
0.15
–70
4
0.3
6
0.1
3
0.3 7
0.1
0
0.40
0.10
0
.
4
1
0.0
0.4
9
0 2
–1 .08
0
00 .43
0.
07
30
0.2
20
–6
–1
0
32
18
0.
0.2
600
0.
.47
0
–10
0.2
6.0
0
2 GHz
0.1
6
0.3
4
10
0.24
0.23
0.26
2
0.2
0.27
8
10
0.2
20
(
70
1
0.2
9
0.2
0.1
3.
0
0.3
0.8
30
200 MHz
0.15
0.35
0
0.2 0
VCC = 5.0 V
0.14
0.36
80
–5
90
0.3
50 MHz
0.13
0.37
4.0
0.
WAVELE
NGTH
S TO
WAR
DG
0.0 ENERA
3
TO
0
T IN D
0.0 R
EGR .47
4
EES
0.
1.
0.25
0.25
T
EN
0
0.26
0.24
0
0.12
0.38
3.
0.24
0.26
0.6
6.0
0.3
0.8
2
12
0.6
0.2
2
0.11
0.39
100
40
0
0.01
0.49
0.02
0.48
0
0.49
1
0.48
LOAD
2 RD0.0
0T.0
OWA F REFLECTION COEFFCIEN
0.4
0
0.4
0.
0. 06
44
2.0
5
0.
0.6
1.8
50
19
0. 31
0.
4
0.4
1
0.4
0.2
1.6
0.2
1.0
0.9
0.8
1.4
0.7
0.1
0.3 7
3
0
.2
7
0.2
0.23
8
0.2
2
–20
.08
)
600
–10
0
0.10
0.40
110
0.23
0.27
REACTANCE COMPONENT
R
––––
0.2
ZO
0.1
6
0.3
4
10
0.2
70
8
20
0.1
0.15
0.35
0.
0. 31
19
.09
2.0 MHz
0
0.
–4
07
0. 3
4
0. 0
13
VCC = 5.0 V
0.14
0.36
80
0.2
00 9
0.2
0.3
1
–3
0.2 0
0
0
0
T
EN
0.2
(
0.13
0.37
1
0.2
9
0.2
30
8
4
90
0
0.2 0
0.3
0.3
0.
0.12
0.38
40
0.3
07
0. 3
4
0. 0
13
0.11
0.39
100
20
8
0.0 2
0.4 20
1
0.10
0.40
110
50
9
0.0
1
0.4
19
0. 31
0.
.47
Figure 18 (a). S11 vs. f Characteristics of µPC1675G
0.
0.
18
32
50
Figure 18 (b). S22 vs. f Characteristics of µPC1675G
0.
0.
18
32
0.37
0.13
0.35
0.15
0.36
0.04
–80
–90
0.38
0.39
0.12
0.11
–100
0
–11
–70
4
0.3
6
0.1
1.4
1.6
0
3
0.3 7
0.1
–6
1.8
0.2
32
18
0.
0.40
0.10
0.4
1
0.0
0.4
9
0 2
–1 .08
0.
20
4
0
00 3
.0
7
30
1.2
2.0
1.
0
–1
0
1.0
0
0.9
0.6
3.
0.8
0.8
4.0
0
1.
4
50
20
10
5.0
4.0
3.0
2.0
1.8
1.6
1.4
1.2
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
(
0.2
0
1.
)
2.0
5
0.
0.6
1.8
1.6
0.2
1.0
0.9
0.8
1.4
0.7
0.37
0.13
0.8
1.6
0.7
1.4
1.2
1.0
0.9
0
0.6
1.8
2.0
5
0.
44
0. 06
0.
–1
0.2
0.2
0.6
0.
0. 31
19
NE
G
0.4
0
0.6
0.
–4
0.7
)
6.0
–11
0.38
0.39
0.12
0.11
–100
–90
0.36
0.04
–80
0.35
0.15
–70
(
)
OM
EC
NC
TA
–
AC – JX
–
E
–
R
– ZO
E
IV
AT
40
–1
NE
G
0.4
0.
0. 06
44
1.
0
T
NEN
PO
10
0.0
0.4 5
5
50
20
10
5.0
4.0
3.0
2.0
1.8
1.6
1.4
1.2
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1.2 GHz
100 MHz
50 MHz
0.
3.
0
1.
0
4.0
6.0
200 MHz 1.2 GHz
)
8
0.
0.2
8
0.2
2
–20
(
REACTANCE COMPONENT
R
––––
0.2
ZO
50
0.40
0.10
0
.
4
1
0.0
0.4
9
0 2
–1 .08
0
00 .43
0.
07
30
4
0.3
6
0.1
0.2
0.
8
0.6
0.1
0.4
20
10
6
50
0.
0.1
0.3 7
3
0.2
00 9
0.2
0.3
1
–3
0.2 0
0
0
0.
5
100 MHz
20
0.2
20
0
0.2
600
–5
0.1
6
0.3
4
3
0.3 7
0.1
0.1
0.4
0
0.6
15
0.6
POS
14
ITIV
0
ER
EA
CT
A
––+JX NCE
–
ZO –
CO
M
PO
N
0.8
0.1
8
0.
4
0
1.
(
)
POS
14
ITIV
0
ER
EA
CT
A
––+JX NCE
–
ZO –
CO
M
PO
N
0.2
6.0
8
200 MHz
50
0.4
0.26
0.24
T
NEN
PO
OM
EC
C
N
TA
AC – JX
––
RE
––ZO
E
IV
AT
4.0
0.25
0.25
0.6
0.27
0.23
44
0. 06 40
0. –1
0.
0
0
–10
6
0.4
4 E
0.0WAV
50
–1
1.
0
5
0.4 5
0.0
4
WAVEL
0
10
0.24
0.23
0.26
2
0.2
0.27
8
10
0.2
20
(
3.
1
0.2
9
0.2
0.1
70
–6
0.
ENGT
HS
0
0.01
0.49
0.02 TOWARD
0.48
0
0.49
0.01D
0.0 GENE
7
0
2
.4
3
A
RA
O
.0
8
0.4
L
0 WARD
0.4
O
REFLECTION COEFFCIENT IN
0.0TOR
3
6
7
DEG
0.0GTHS TANGLE OF
4
0.4
R
EES
0.4
0
LEN –160
4
E
0
6
0.0
0. WAV
5
15
0.4 5
0
0.4 5
5
0
–1
5
0.0
0
1.
0.3
0.8
30
7
0.4
O
REF
3
0.0GTHS TANGLE OF
LEN –160
0.4
40
VCC = 5.0 V
0.15
0.35
0
T
EN
0.14
0.36
80
32
18
0.
90
0
0.2 0
0.3
50 MHz
0.13
0.37
0.
0
3.
0
12
0.12
0.38
4.0
2
1
0.11
0.39
100
6.0
0.3
0.8
0.2
8
0.2
2
–20
0.4
0.6
0.26
0.24
0.6
0.27
0.23
WAVELE
NGTH
S
0.02 TOWARD
0.0 GENE
0.48
3
RA
FCIENT
0.4
0.0TOR
IN DE
7
4
GRE
0.4
ES
0.4
0.25
0.25
0.4
0.
0. 06
44
2.0
5
0.
0.6
1.8
50
19
0. 31
0.
0.3
0.4
0.2
1.6
0.2
1.0
0.9
0.8
1.4
0.7
0.1
0.3 7
3
–10
.08
)
600
–5
REACTANCE COMPONENT
R
––––
0.2
ZO
0.1
6
0.3
4
0.2
00 9
0.2
0.3
1
–3
0.2 0
0
0
0
0.10
0.40
110
70
0
0.1
0.15
0.35
0.
0. 31
19
07
0. 3
4
0. 0
13
VCC = 5.0 V
0
0
T
EN
0.14
0.36
80
10
20
0.24
0.23
0.26
2
0.2
0.27
8
10
0.2
20
(
0.13
0.37
1
0.2
9
0.2
30
4
0.
–4
.09
90
0
0.2 0
0.3
0.2
0.3
0.12
0.38
40
0.2
07
0. 3
4
0. 0
13
0.11
0.39
100
20
8
0.0 2
0.4 20
1
0.10
0.40
110
50
9
0.0
1
0.4
19
0. 31
0.
0
0.01
0.49
0.48
0
0.49
0.01
0.0W2ARD LOADLECTION COEF
Figure 18 (c). S11 vs. f Characteristics of µPC1676G
0.
0.
18
32
50
Figure 18 (d). S22 vs. f Characteristics of µPC1676G
0.
0.
18
32
9
4.
PRINTED PATTERN MOUNTING EXAMPLE
The µPC1675G/µPC1676G/µPC1688G are wideband amplifiers of simple construction with only four pins: input,
output, power, and GND.
Because the upper-limit operating frequency is as high as 1900 MHz TYP. in the case of µPC1675G and 1200
MHz TYP. with the µPC1676G, the frequency characteristics substantially vary depending on the conditions of the
print pattern (especially at high frequencies).
Figure 19 shows these variations in the characteristics of the µPC1675G. Print boards A, B, and C in this figure
are:
Board A :
Double-sided copper clad epoxy glass board with GND on the back and front surfaces connected, and
a GND line inserted between input and output to provide an isolation effect.
Figure 20 shows an example pattern.
Board B :
Board A without GND line between input and output.
Board C :
Board B without GND on back side.
As shown in figure 19, a print board equivalent to A is necessary because of peaking in the vicinity of f = 1 GHz
and an increase in the frequency characteristics. The GND line between input and output has an especially important
effect. Board A is used to measure characteristics in Chapter 3.
Figure 19. Mounting Characteristics Example of µPC1675G (GP = 13 dB)
20
VCC = 5 V
TA = 25 ˚C
Power gain GP (dB)
15
Board A
10
Board B
Board C
5
0
0.1
0.2 0.3
0.5 0.7 1
Frequency f (GHz)
10
2
Figure 20 (a). Pattern Example (Top View)
Figure 20 (b). Mounting Example (Top View)
Chip capacitor
IC
Input
Output
OSM connector
OSM connector
Chip capacitors
VCC (Supply Voltage)
Figure 20 (c). Operation Circuit
VCC
1000 pF
1000 pF
Input
Output
1000 pF
11
5.
APPLICATION EXAMPLE
(1) Buffer amplifier for prescaler
The input sensitivity of 1-GHz-class prescalers used in UHF and VHF TV tuners has recently increased. Even
so, a buffer amplifier is connected in the stage preceding these prescalers. The purpose of this is to decrease
coupling with the local oscillation stage and to improve isolation after the oscillation stage and prescaler.
Figure 21 shows the sensitivity characteristics when NEC’s µPB568G 1-GHz prescaler is used, and Figure 22
shows a circuit example. As the load on the µPC1675G/1676G, a 51-Ω resistor is connected to GND. Values
of 50 to 200 Ω are suitable for this resistor. Because the saturation output of the µPC1675G/1676G can be kept
to 4 to 5 dBm, overload input to the prescaler can also be prevented (usually, a prescaler does not divide the
frequency when an input higher than 8 to 10 dBm is applied).
As another local oscillation peripheral, the amplifier IC can also be used as a buffer amplifier to the MIX stage
to prevent oscillation drift when a high input is applied to the antenna (Figure 22).
Figure 21. Input Sensitivity Characteristics of µPC1675G/1676G + Prescaler µPB568G
Input sensitivity Pin (dBm)
0
–20
µ PB568G only
–40
µPC1675G +µ PB568G
–60
–80
µ PC1676G +µ PB568G
1 100
200 300 500
1000
Input frequency fin (MHz)
2000
Note µPB568G has been discontinued.
12
Figure 22. Prescaler Buffer Amplifier
RF amplifier
MIX
Antenna
input
To IF
+B = 5 V
Buffer
amplifier
Prescaler
1 000 pF
Local
OSC
(VHF)
UHF
local
1 000 pF
1
8
2
7
3
6
4
5
OUT
Approx. 50 to 200 Ω
Coupling capacitance
can be reduced.
(2) Cascade amplifier
The input/output impedance of the µPC1675G/1676G/1688G is matched to 50 Ω so that multiple amplifier ICs
can be connected.
Therefore, the amplifier ICs can be used as a cascade amplifier.
Figure 23 shows an example of the characteristics of two µPC1675Gs connected in cascade. For the print pattern,
a double-sided copper clad epoxy glass board is used as described in Chapter 4, and the input and output are
isolated by the GND line.
The µPC1676G is a high-gain type IC. However, because of peaking at f = 700 MHz, the targeted characteristics
must be considered of the combination.
.
As a combination to produce output PO =. 10 dBm, use the µPC1675G + µPC1658G.
Figure 23. Cascade Amplifier Characteristics of Two µPC1675Gs
40
VCC = 5 V
TA = 25 ˚C
GP
20
10
NF
10
5
0
Noise factor (dB)
Power gain GP (dB)
30
0
0.1
0.2 0.3
0.5 0.7 1
2
Frequency f (GHz)
13
[MEMO]
14
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CS 95.11
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M4 94.11