NTE851
Integrated Circuit
VHF/UHF Prescaler
Description:
The NTE851 is an integrated circuit prescaler in a 14鈥揕ead DIP type package intended for use in TV
frequency synthesis tuning systems over an input frequency range of 90 to 1000MHz. It performs
division by 256 in he UHF mode and division by 64 in the VHF mode.
The mode of operation can be selected by means of the bandswitch and the separate UHF and VHF
input pins provided. The output is a complementary emitter鈥揷oupled stage with controlled slew rate
for harmonic suppression.
All input pins should be AC coupled to the appropriate input signal source. Because of high sensitivity,
unbuffered coupling from the local oscillator is possible in most cases. In the UHF mode, which is
activated by applying a high level to the bandswitch input pin, all eight divider stages are operative,
resulting in division by 256. In the VHF mode, activated by a low level at the VHF input pin, two divider
stages are bypassed, resulting in division by 64. As a result, approximately the same range of output
frequencies are generated fo both the UHF and VHF TV bands. An internal amplifier/multiplexer pro-
vides this control while isolating both inputs and amplifying the VHF signal. In addition, hrmonic output
is reduced above 40MHz by limiting output signal rise and fall times and maintaining a balanced load.
Features:
D
Broadband Operation: 90 to 1000MHz
D
High Sensitivity
D
Standard 5V Power Supply
D
Dual Mode Operation: VHF/UHF
D
Complementary ECL Outputs
D
Independent VHF & UHF Input Pins
Absolute Maximum Ratings:
DC Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5V
DC bandswitch Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V
RMS Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500mV
Device Dissipation (T
A
鈮?/div>
+70擄C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600mW
Derate Linearly Above 70擄C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5mW/擄C
Operating Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0擄 to +70擄C
Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 鈥?5擄 to +150擄C
Lead Temperature (During Soldering, 1/16鈥?from case, 10sec max) . . . . . . . . . . . . . . . . . . . . +265擄C
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