SL2035

The SL2035 is a bipolar, broadband wide dynamic range mixer oscillator, optimised for applications as the downconverter in double conversion tuner systems. It also has application in any system where a wide dynamic range broadband frequency converter is required.

The SL2035 is a single chip containing all necessary active circuitry and simply requires an external tuneable resonant network for the local oscillator. The block diagram is shown in Figure 1 and pin connections are shown in Figure 2.

In normal application the signal of SL2035  from the high IF output is connected to the RFIN and RFIN inputs. The RF input preamplifier of the device is designed for low noise figure within the operating region and for high intermodulation distortion intercept so offering good signal to noise plus composite distortion spurious performance.

The preamplifier SL2035 also provides gain to the mixer section and back isolation from the local oscillator section. The approximate model of the RF input is shown in Figure 3.

The output of the preamplifier SL2035 is fed to the mixer section which is optimised for low radiation application. In this stage the RF signal is mixed with the local oscillator frequency, which is generated by an on-chip oscillator. The oscillator block uses an external tuneable network and is optimised for low phase noise. A typical application of SL2035 is shown in Figure 5. This block also contains a buffer-amplifier to interface with an external PLL to allow for frequency synthesis of the local oscillator.

The IF output of SL2035 can be loaded either differentially or singleended. It is recommended that the differential load as in Figure 5 is applied as this gives best noise performance. If the output is loaded single-ended the noise figure will be degraded. The approximate model of the IF output is shown in Figure 4.

In application care of SL2035 should be taken to achieve symmetric balance to the IF outputs to maximise intermodulation performance.