Wide band 10MHz 500MHz RF amplifier

This paper describes an RF amplifier circuit which is suitable for the frequencies between 10MHz and 500MHz. These kind of amplifiers are called wide band amplifiers. Wide band amplifiers are used in communication receivers, RF measuring equipment and tons of other devices. The circuit described here uses a state of the art transistor to get maximum performance at high frequencies. It can be used as a low noise pre-amplifier due to his low noise characteristics.

This is a classical RF amplifier design. The feedback resistors R3 and R2 define the gain. By changing the values we can get a higher gain at low frequencies, but this will influence the overall gain taper of the amplifier. Coil L2 is used to get more gain at high frequencies. If the value is increased, instability will occur. Dimensions of L2 are: 6 windings, inner diameter is 3mm and wire thickness must be 0.4mm. In the proto type I used and SMD type for L1, make sure it’s a high Q coil. The transistor, which is used here, is a wide band transistor with an Ft of 9 GHz. Like in all other RF circuits make sure that the connections are short as possible. Supply voltage : +12V Current : 10mA Input / output impedance : 50 Ohm Frequency range : 10MHz 500MHz Noise figure : 3.5dB typical IP2 : 110dBuV IP3 : 105dBuV

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