With the continually dwindling selection of through hole small signal parts some designers and builders are looking to make the jump to SMD components. This is of interest to me but I lack the familiarity to just jump into SMD without a little guidance. While some common through hole parts are available in surface mount packages there are quite a few, especially newer devices, only available in SMD packages. That said, I'd like to engage those already familiar with SMD choices to help create a list of staple devices the DIY'er may just want to stock up on.
I'd like to suggest making recommendations based on suitability for various applications in typical topologies, ease of access (i.e. highest availability), and ease of use (i.e. those in 'larger' SMD packages). It might also be nice to draw approximate equivalencies between TH and SMD parts if such information is not obvious. Recommendations for applications the likes of input, VAS, cascoding, current sources / sinks, current mirrors to pre-driver / driver applications and in various technologies such as BJT, JFET, MOSFET.
I will start off, as below. Any one care to make a few suggestions? I can keep a list here in Post#1.
Device Type - Manufacturer - Part Number - Package - TH Equivalent - Application (Characteristic)
----------------------------------------------------------------------------
BJT (NPN) - NXP - BC817 - SOT23 - BC337 - Current Mirror (Low Vce)
BJT (PNP) - NXP - BC807 - SOT23 - BC327 - Current Mirror (Low Vce)
I'd like to suggest making recommendations based on suitability for various applications in typical topologies, ease of access (i.e. highest availability), and ease of use (i.e. those in 'larger' SMD packages). It might also be nice to draw approximate equivalencies between TH and SMD parts if such information is not obvious. Recommendations for applications the likes of input, VAS, cascoding, current sources / sinks, current mirrors to pre-driver / driver applications and in various technologies such as BJT, JFET, MOSFET.
I will start off, as below. Any one care to make a few suggestions? I can keep a list here in Post#1.
Device Type - Manufacturer - Part Number - Package - TH Equivalent - Application (Characteristic)
----------------------------------------------------------------------------
BJT (NPN) - NXP - BC817 - SOT23 - BC337 - Current Mirror (Low Vce)
BJT (PNP) - NXP - BC807 - SOT23 - BC327 - Current Mirror (Low Vce)
Hi Jason
Good idea...
I've been playing around with SMD passives ever since Gareth (Bigun) gave me the idea.
The 1206 package is very easy to work with - a little practice and you will place and solder these faster than their through hole equivalent. I like 1206 resistors for the higher Pd ratings, unfortunately quality thin-film variants are a little difficult to source here in Australia, and I've started moving to 0805, simply because the range is better.
The Susumu RR series have decent specs and are cheap.
For transistors it is best to stick with SOT-23 parts; I'd say most of not all of the 6 pin packages are too small for the majority of DIYers to hand solder.
For general purpose transistors I suggest BC846B (NPN) and BC856B (PNP) which are equivalent to BC546B and BC556, respectively. These have a Vceo of 65V so quite suitable for most positions in small to medium power amps.
If higher breakdown voltages are required then there is the MMBT5401/5551, which are (you guessed it...) equivalent to the 2N5401/5551 and are rated to 160V.
Its worth noting that these SMD transistors have about half the PD rating of their through-hole counterparts. So you may need to redesign the circuit; e.g. the D. Self derivatives usually run pretty aggressive tail currents so this will almost certainly need to be taken into account.
Good idea...
I've been playing around with SMD passives ever since Gareth (Bigun) gave me the idea.
The 1206 package is very easy to work with - a little practice and you will place and solder these faster than their through hole equivalent. I like 1206 resistors for the higher Pd ratings, unfortunately quality thin-film variants are a little difficult to source here in Australia, and I've started moving to 0805, simply because the range is better.
The Susumu RR series have decent specs and are cheap.
For transistors it is best to stick with SOT-23 parts; I'd say most of not all of the 6 pin packages are too small for the majority of DIYers to hand solder.
For general purpose transistors I suggest BC846B (NPN) and BC856B (PNP) which are equivalent to BC546B and BC556, respectively. These have a Vceo of 65V so quite suitable for most positions in small to medium power amps.
If higher breakdown voltages are required then there is the MMBT5401/5551, which are (you guessed it...) equivalent to the 2N5401/5551 and are rated to 160V.
Its worth noting that these SMD transistors have about half the PD rating of their through-hole counterparts. So you may need to redesign the circuit; e.g. the D. Self derivatives usually run pretty aggressive tail currents so this will almost certainly need to be taken into account.
Member
Joined 2009
Paid Member
Well, I figure if they're still making tubes there will be NOS of through-hole parts for many years, enough to keep everyone happy till we're too old to care. That said, SMD does offer a lot of new stuff to try out and with low cost PCBs available there isn't any real obstacles in the way to going to town on an SMD project. I like to use both, and find that SMD works best with two-terminal devices with through-hole for the rest. Caps especially are hard to do SMD because they are designed to work with an oven-based soldering system so through-hole is certainly preferred.
Hi Christian, I remember starting with the 1206 size so I could weave a pcbs trace underneath them back when I tried making my own pcbs single sided in the kitchen sink. I'm glad you are having fund with those 0805's, they are a perfect size for professional pcbs I- but as you go smaller you give up is the ability to read the part values printed on the part so you have to remain disciplined as to storage. Once you drop a part you pretty much have to write if off as lost 🙂
Hi Christian, I remember starting with the 1206 size so I could weave a pcbs trace underneath them back when I tried making my own pcbs single sided in the kitchen sink. I'm glad you are having fund with those 0805's, they are a perfect size for professional pcbs I- but as you go smaller you give up is the ability to read the part values printed on the part so you have to remain disciplined as to storage. Once you drop a part you pretty much have to write if off as lost 🙂
Last edited:
- Status
- Not open for further replies.