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The other thing is I just downloaded the datasheets for the 2SC2999 and the 2SC1674L and the test conditions for determining noise figure are very different.

In the case of the 2SC1674L the device test fixture is driven directly from a 50 ohm source into the transistor base and uses a 22k resistor for bias within the RF test fixture.

In the case of the 2SC2999 the test jig for noise figure on the datasheet shows a very elaborate design with feedback and also a tapped tuned circuit on the input. This steps up the impedance into the base and this will affect the noise figure of the overall test fixture. It also keeps any bias resistors outside the RF area and this is good for keeping noise low.

So I can't see how you can directly compare the noise figure data for these two devices based on the info in the datasheets.

This is because the figure in the datasheet is the noise figure for the overall TEST JIG CIRCUIT and not some magic figure burned into the transistor itself. The noise contribution from the transistor will vary and will depend on the components around it and the source impedance driving it and also its collector current.

<blockquote data-quote="G0HZU" data-source="post: 327762" data-attributes="member: 19109">The other thing is I just downloaded the datasheets for the 2SC2999 and the 2SC1674L and the test conditions for determining noise figure are very different.In the case of the 2SC1674L the device test fixture is driven directly from a 50 ohm source into the transistor base and uses a 22k resistor for bias within the RF test fixture.In the case of the 2SC2999 the test jig for noise figure on the datasheet shows a very elaborate design with feedback and also a tapped tuned circuit on the input. This steps up the impedance into the base and this will affect the noise figure of the overall test fixture. It also keeps any bias resistors outside the RF area and this is good for keeping noise low.So I can&#039;t see how you can directly compare the noise figure data for these two devices based on the info in the datasheets.This is because the figure in the datasheet is the noise figure for the overall TEST JIG CIRCUIT and not some magic figure burned into the transistor itself. The noise contribution from the transistor will vary and will depend on the components around it and the source impedance driving it and also its collector current.</blockquote>

[QUOTE="G0HZU, post: 327762, member: 19109"] The other thing is I just downloaded the datasheets for the 2SC2999 and the 2SC1674L and the test conditions for determining noise figure are very different. In the case of the 2SC1674L the device test fixture is driven directly from a 50 ohm source into the transistor base and uses a 22k resistor for bias within the RF test fixture. In the case of the 2SC2999 the test jig for noise figure on the datasheet shows a very elaborate design with feedback and also a tapped tuned circuit on the input. This steps up the impedance into the base and this will affect the noise figure of the overall test fixture. It also keeps any bias resistors outside the RF area and this is good for keeping noise low. So I can't see how you can directly compare the noise figure data for these two devices based on the info in the datasheets. This is because the figure in the datasheet is the noise figure for the overall TEST JIG CIRCUIT and not some magic figure burned into the transistor itself. The noise contribution from the transistor will vary and will depend on the components around it and the source impedance driving it and also its collector current. [/QUOTE]

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