Fast switching transistors: PMBT2369 vs. MMBT2369

A project log for Evaluating Transistors for Bipolar Logic (RTL)

Experiments on optimizing discrete logic gates based on bipolar transistors

TimTim 04/01/2020 at 06:150 Comments

As outlined earlier there are still two fast switching transistor types on the market: The PMBT/MMBT2369 and the BVS52. Both are offered by Nexperia and On Semi.

The PMBT2369 is Nexperias offer, my guess is that the "P" stands for Philips. Nexperia was carved out of NXP, which used to be Philips semiconductor branch. Similarily the "M" in MMBT2369 is most likely related to Motorola, which On Semi belonged to a long time ago. The BVS52 seems to be basically the same device at both vendors, so I did not bother investigating it.

I compared On Semis and Nexperias flavors of the 2369. As you can see in the table above, their datasheet values are basically the same. I measured hfe and found the onsemi device to have slightly higher gain.

The plot above shows a comparison of both devices. It appears that the PMBT2369 is quite a bit faster. The MMBT2369 shows a maximum at around 5V supply. At higher voltage (current), the saturation charge seems to dominate switching behavior. This trend can only be seen at >8V for the PMBT2369.

Minimum tpd of the MMBT2369 based RTL inverter is 6.8 ns, that of the PMBT2369 based inverter is 4.8 ns.

It's quite difficult to asses the actual origin of the speed difference, just speculating: The higher current gain will increase the miller capacitance of the MMBT2369. However this is mostly relevant while the device is turned on. The critical condition is the storage time of the saturation charge, which flows out of the base when VBE is already zero and the miller capactance plays no role.

The PMBT2369 definitly appears to be the faster of the two. In fact, the PMBT2369 seems to be the fastest bipolar switching transistor that is still available in high volume today.

Why even look at other devices? Unfortunately it seems that the PMBT2369 is only available in the relatively large SOT23 package. To build dense discrete logic (yes, it makes no sense, I know), it would be of interest to use much smaller packages such as SOT523 or SOT723.